BTW Adnoh - I am my Engine builder. I've built a couple dozen 2-strokes mainly twins but a handful of singles. I do my best with:

Shop press and pullers
Freezer and heat gun
Slide hammers and regular hammers
Files and sanders
Dremel with 90 degree angle
Threebond 1211
Threebond 1217H
Loctite variety (Including sleeve retainer)
Marine grease
Full tool set(s)


I'm starting to assemble the bottom end already. I put the crank in the freezer after I took the pictures, and within an hour I had both cases and crank together (Where I previously installed the new bearings about a week ago). New case gasket dressed with 1211. Rubber bands holding the rod in place. Crank bearings and seals are installed. Seals get back-filled with grease and 1211 around the case/seal for a better long term seal.

Case bolts torqued to 10lb (Most of the 10mm bolts I tq to 10lb)

Also already have new bearings/orings for the balance shaft. Balance shaft is installed with loctited retainers. Balance drive gear is installed - and yes a new O-Ring is behind it. Torqued to 87lb and pinned (locked). Note for some this is a reverse thread 1-5/8" nut (41mm?).

Starter is installed with new oRing.

Next is the mocking up a first asm install of the piston, top end bearing, base gasket and cylinder WITHOUT the piston rings. Tighten cylinder to bottom end (Dry fit).

I intend to have the ports degree'd shortly. Wheel is installed.


About the only thing I've never done is actually port a cylinder, but I feel confident moving forward and learning. Oh I cant rebuild bottom cranks and I don't have a bore/hone machine, but those I've solved by the use of other's services.

That being said - thank you very much for your help with porting education!

Updated information (Very exciting)! I measured this stuff around 4 times. Here is what I've come up with:

TDC (Top Dead Center) Piston to Deck : 11 Thousandths (.28mm)

BDC Port 'Lip" 0.76mm (.4mm on one of the rear transfer ports). All ports have a lip, meaning the piston is going further DOWN than the port. I'm pretty sure port bottoms can be lowered to match the piston at BDC, up to 0.76mm. that's got to account for something positive. The piston skirt is about 2mm under the lower exhaust port.

Exhaust opens at 92* for a duration of 177* to the nearest degree

All transfer ports from what I can tell open at 123* for a duration of 117* to the nearest degree.

Blow-down duration is 32*

Many of these ports can be widened. There is quite enough room around the locator pins. The new crank is nice and tight there no rotating this piston at all (margin for locating pins is WIDE)

My pilot had two filters when I bought it. I replaced them both with serviceable see-through filters with 5/16" fittings. This was before the tare-down and rebuild - and both filters did actually catch stuff before; though my tank was badly rusted and full of silt/dirt and the original fuel pump was nasty. The bottom one almost completely filled up with yuck last ride before getting my tank re-finished. The top one had a little; nothing to call home about but glad it didn't go in the carb.

I might remove the top filter later on. Depends on what kind of tested flow rate I can measure.

I was able to alter/port all ports to get some desirable durations ex/tr/bd. I'm very very close to 184/124/30 now. Ex and BD are right between 183-184 and 29-30*

I also fixed up some of the sleeve mismatching as well as widened the exhaust port 2mm on each side. Re-shaped the top, and also dropped the bottom sides about 1mm as well - so the port looks more square than oval now. In all I raised the intake ports about 1mm and the exhaust port about 2mm. I ported based on desired port duration; marking the cylinder about 5-times during each dry assembly (Piston without rings makes on/off a lot easier). Also carved out what I believe some call Honda Bumps in the exhaust. Porting and re-chamfering took about 4 hours. I probably could have gone further with widening, angling, and re-shaping but I just decided to stop where I was. Maybe next time I'll port further when I'm at 82mm.

I hope and think this thing is gonna rip!

I was also able to fully assemble the Engine and am happy to say it passed vacuum pressure test of 3inhg tonight. It held for several minutes. Once the threebond 1211 gasket and seal dressing cures over night I'll test again with stronger vac/pressure test of about +-6 psi/inhg.

Everything went together perfectly and as planned. No spare parts that I didn't plan on, and every new part was used exactly. Everything is back together from the power bloc, to the pull start, intake, exhaust header, starter, and KFab head.

You might think I assembled this thing quickly/haphazardly; but really I've been planning and cleaning parts in my free time for the last 2-3 weeks!


Pulling the rip cord (well, ok theres probably a bunch of 2-stroke lube in there from assembly) feels like this Engine has LOTS of compression!

Squish measured out to be 42.5 thousandths


Tomorrow if time permits I'll be cleaning the Pilot in preparation for Engine re-install.

Nice! Great job dude!

You couldn't ask for better help than Adnoh!

Its gonna rip! Hope you weren't planning on steering with the front wheels! lol!

Man I wish I could have got to you before you buttoned it up.
No big deal.
Thanks for the kind words bull.
Next time you open it up you can work on time / area.
The port timing changes you made are step one.
Two late for step two.
Step three would have been to set it at each mean line drop in a piece of paper and map the area. Then transfer to mm squared paper and count the area or squares. Change to cm3 and check the angle area.
Then a time area for that port can be done. Once that is complete then your do final port work. Blow down 29 can be corrected on next top end removal if required. Heck gaskets are cheap after you take it out and get a feel for it.

Pretty cool what you have done and took time to do. It will pay off. Have you ran your your final CR and UCCR numbers.
I would say once it's toghter you can look at the intake set up.
Two schools of thought.
High velocity
Low velocity

This will dictate the multiplier for carb and tip ratio for reeds. This will impact your port work based off of primary ratio and it's ratio to secondary.
Again don't make to much of it, it's not that hard.

Let's look at what we know:
Stock 89 carb (90 would be better for mid range set up)
V- force reeds set in factory position.
No change in primary.
Change in port timing°
Some kind of dual intake set up (filter)

So:
The cfm of carb fixed, cfm of Engine changed. ( Ported)
Reed velocity across tips changed, time area changed for Reed lift.
This will push you towards a high velocity.
That is where the great debate comes in.
Now., If this was offset with a change in primary some how it could be brought back down for a smoother power delivery. Remember we're a CVT based Engine.
This could also mellow out the reeds for a given velocity.

So I would take a reverse approach to stuffer crank.
As a stuffer add CR we would removal CR for the case.
Heck we're already at 4500 rpm so we don't need more.

I would think we need to change it in way of larger carb and increased Volume on the primary. Don't take much.

More in this later have to go.

Good job zero. Thanks for letting me bla bla bla.

Adnoh

Thanks and appreciate it. I did widen the rear transfers a bit and reshaped the exhaust slightly. I’m figuring I adddd 12% surface area to the exhaust, and 7% to all transfers. I may have raised the angle of the transfers slightly but mainly because my tools for porting did what they could.

I forgot to get final numbers to calculate CR figures. I’ll get that later today. Hope to also get a compression test before and after first heat cycle today/tomorrow and dial- in the carb pilot jet.

Speaking of jetting, I’m guessing the pilot is going to be a little too rich and the main is going to either be on par or maybe slightly lean. Needle is probably ok where it is.

PE34
50 Pilot jet
Air screw at 1&5/8 turn
145RD main jet (Whatever RD means)
35A needle at -1 leaner from middle

I got the Engine and fuel tank back installed. I have the carb and exhaust ready to go also. I pulled out my radiator and overflow bottle for deep cleaning.

BTW the overflow bottle on this thing looks home-made. Someone made a it almost look factory out of some sort of cylindric metal catch can thing. It almost looks like an oil catch can with some home-made welds. Looks good to use but unfortunately I can never tell home much coolant is actually in it as it is completely solid. Maybe I can put a couple of T-fittings with clear tubing somehow so that I can see its level from looking at the hoses.

Black sludge came out of the radiator, and a lot more came out of the overflow bottle. It was so nasty it reminded me of a head gasket failure gone bad on a car.


Recalling Engine tare down, I did find milky white oil inside the front cover/stator section. It was obvious water was leaking into there, though no large components were failed. The water pump water seal - mechanical seal, was destroyed, and the small oil seal behind it was also questionable and so; its possible cooling water/coolant was seeping into the front cover; and vice versa - oil into the cooling system. Someone had actually plugged the middle drain with silicon or something as that should have never happened (mixing) with an un-obstructed drain hole - but in this case mixing did happen.

Its fixed now; thank goodness nothing was harmed. I'd say there was a list of ticking-time-bombs awaiting this Engine's final state. Good thing no fires were lit! I saved a lot of cost in rebuilding this thing.:

1. Carb leaking from the bottom 17mm bolt
2. Rear main seal leaking
3. Rust in the gas tank
4. 1/2 operating original fuel pump
5. Water mixing the oil
6. Low coolant level when I got it
7. Oil mixing with water
8. Ring end gap at ~3x service limit
9. Rings capable of curling past locator pins
10. Signs of preignition
11. Rear bearing (Koyo) turned BLUE from air leak - surprised it held together <-- This one would have ruined EVERYTHING
12. Bottom bearing was probably original and VERY worn
13. Connecting rod - signs of blu-ing and probably original
14. Top-end bearing worn
15. Chinese Front main bearing
16. Rust clogging both original fuel filters (The fist filter in-line had actually torn and was done+DONE - Probably destroyed the fuel pump
17. Piston at 2~3x clearance service limit



Tonight I'm going to complete install of the carb, drive belt, and guard, and maybe the exhaust and then that's about it. Today is actually the first day I'm tired of working on this thing. I hope to get it in a start-able state for tomorrow.

Then I gotta install the seat/harness, belly pan, and re-tighten the front brakes. Should be ready for next weekend!

Alls that is left now is new coolant, seat, seatbelt and belly pans. I put a couple gallons of 36:1 mixed C12 110 octane in the tank and checked for leaks at my old & new pickup fittings. Front brakes are going under the knife again - I want them stronger.

I was unable to test start the Engine today as its raining badly here in the deep south. I am hopeful I can do the first heat cycle tomorrow.

You mentioned that low coolant . Keep eye on it in case its a sealing issue. By chance you lap head and top of cylinder before assembly?

You say two gallons on fresh tank clean
That I just one gallon over reserve with new pump. Make sure you on reserve if your going to run with that much fuel. I always recommend full tank or at least four gallons.

Food for thought as well. Your needle position is one lean. I would recommend one rich from center with main jet removed. This will ensure your needle is Rich enough and also provide you with a throttle position for that needle and when it gets on the main. Then you can adjust if it's too fat off idol and then go to main jetting. Also if there is an issue you can go WOT (Wide Open Throttle) for a very over rich mixture to save Engine. Your going to spend a lot of time on the mid so jet for it. I here a lot of pilots too lean after a hard pull. Scars me to death. Here a wierd one but works gap the hell out of the plug ( snuff the spark) and it with miss fire going rich if the pressure gets to high . Then back down gap as your ready for main jetting or even a nine plug. You running high preformance water craft has a great understand ing of this already just wanted to throw a reminder out there.
It's a different animal now.
RD is a generic jet. Way be off from from kehin. I use them too just not next to non RD. Like 152 155. Your main also should run higher than 145. Been wrong before. Again each one different. I would think in the high 150s or even 160 ranges. Again it takes what it takes.

Good luck and look forward to the report. A crank reading too would be nice cold and warm. Gauge good? If low check the shrader valve in the guage also if hose the valve need to be in the end of hose section or you need to add for the hose in ccs

Thank Adnoh.

I'm going to fill the tank. I just didn't want my new pick-up leaking. Also I'm pulling fuel straight from the bottom of the tank - not the stock pick-ups. I put a 5/16" 90 degree brass fitting with an in-tank filter at the bottom where normally the drain plug is - as I didn't trust the stock pickups. I also don't trust fuel On/Off/Res selectors - they are usually the cause of jet-ski Engine lean failures in my other world. The fuel stops when the pump stops, and if the carb needle decides to let go - well that's just it's time to get a rebuild in there. I expect it may drip a little but its better than mis-trusting a fuel selector.

The Engine was running very rich before rebuild - the plug was pretty crusty black after just a short ride then but that could have been a health issue anyways.

Do you really think I need like a 155 main jet? I'll lift the needle. Have a Keihin jet collection. I'm getting a pyrometer too but I don't think I'll have time to install it. We'll see. Do you know how far down the exhaust it needs to be installed?

New coolant is staying perfectly level. Here a few pictures including the homemade overflow bottle. I put a side tube to measure it's fullness. I also pressure tested the Engine's water jacket after assembly. It held 10 PSI perfectly. Again I think the low coolant before rebuild had to do with a torn mechanical seal on the water pump.

Tonight I ran a cranking compression test - full battery, known good gauge, full throttle, crank till it stops moving...blehbleh... It pumped 180 psi - and that is BEFORE break-in. I have not yet started the Engine. It is possible there is some 2-stroke assembly lube helping it out a bit. Reminder running 110 C12 race fuel. The
new fuel pump is working - it lifted plenty of fuel up to the carb as it filled both fuel filters very quickly.

Nothing is leaking.

I'm thinking before - when the exhaust port was a couple mm lower than it is now - cranking compression might have been higher than that on the last rebuild.

Pics

Actually you are probably right on the jetting being wrong. Stock this thing runs with 52/140 jetting, and since its at 50/145, I'm sure its lean especially now with the porting, plus the pipe, head w 47cc dome, bore, tightness of squish and all other parts new, etc...

I'll raise the needle to +1 rich and put a 162 main jet in for break-in. I think I may have other needles to try also. I'll know quick if that's too much but since its like 10 minutes to swap jets no big deal. I've never run anything without a main jet. Interesting - I may try it.

I was going to start with BR8ES spark plug, but given its a little higher on dynamic compression (PSI) I'll start with a BR9ES. I have a collection as jetskis run similar ranges 7 thru 9.

Your right on with the fuel selector on the ski. Mine went by bye too .
The pilot , I do not ever recall having an issue.
Crank pressure sound in line with numbers. What's cool is it leaves you room to raise the exhaust if need be.
Jetting as you know is just a guess untill you run it. I'm very confident you have a handle on it.

One item to note is the rings. The wiesco will four cornor if to much heat is applied untill they seat a little. The eight will wick more heat into coolant. So make sure it's up to temp before to much load is applied. And be careful not to load to long with a quick unload. This is where is four corners. A lot of guys will pull choke on deceleration and bleep throttle to load up a little. After a tank it game on if crank numbers hold. I do both cold and warm during heat cycles then after a run do the same and add cap of oil to verify it's in line.

Looks good
Look forward to ride report.
If all goes well we should ask "H" to move this post to projects for future reference for others.

Definitely. One thing to note is, I'd really like to upgrade this PE34 carb to something bigger. 2 weeks ago I had my eye on a PWK42 Pro Circuit carb which seemed to be on sale for $290 from places, which was less than a PWK38/39 - but then Sudco supplier ran out of them...

Since I've got upgrade in scope; I'm not actually going to put a whole lot of time in fine-tuning this PE34 - I plan to run it RICH and hope it doesn't dog down much; for the first tank (as I do want to PLAY and not foul out) - and then swap out to a larger carb after break-in.

I'm trying to get some VE figures for this Engine though - to be sure which carb would work and not be too large. Seems with a peak rpm of 7500, and a VE range of .65 ~.90 this PWK42 would be -ok-, but at 6500rpm it may be a tad large. Any suggestions?

I also want to rebuild my Works shocks at some point soon (Probably during jetski season)

For that set up 38 mm with high velocity intake. 39 ok . 41/42 to large. Never hurts to try though.
Once you get the stock set up it will help in the decision. Next time you pull reeds block flip it over and look to see which way is better for intake boot. If boot is good some mod can be done to help flow.
This looking down the tube. The two diff angles of the v force is a good for mid and high rpm.
I run 39 on mine and wife's for hers it would like a 38 however I keep them the same for simplicity. Your air cleaner set up will play into it as well. You know what to listen for there. Gotta love the sound of those reeds when in frequency. As a comedy guy says there's your sign . The Engine in it's tune with a given frequency. It's the nature of things.
Now I'm bla bla bla.

Time for more fun math: Carburetor Sizing, Back Yard Hacker style.
From tuners hand book we can use as a guide.
We need:
Cylinder Bore, (K), peak power in RPM to find D
Bore: 397 cc or CM-3
(K): we have to find using base line
Peak power: We use Lee’s post and a stock port map using sec-cm3 or 6800 rpm
Using the stock book as a base line we know
D=: 32 mm
Now we will use this information to find Base Line (K)
Now for fun stuff!
We need to turn CC’s or CM-3 into liters. Easy to do we divide CM-3 by 1000.
397/1000= .397
Next step is to take .397 (liters) times peak power or 6800, 6800 x .397= 2,699.6
Next we use the SQRT button to get 51.9576 which we round up to 51.96 Call this SQRT -1
Now we need to find (K) for the 32mm carb. Or 32/51.96 =.6158 round up. So (K) =.616
Now for new carburetor we need to find a new (K) based on a ratio of the SQRT for new Engine.
New Engine:
Bore 412 cc or CM-3 =litters .412
New port timing peak power of 7800 rpm based from SEC-CM3
7800 x .412= 3,213.6 SQRT=56.688, round up to 56.69. Call this SQRT-2
Now we take SQRT-2/SQRT-1 to get a ratio of change.
56.69/51.96 = 1.091
Final steps: Run carb size using SQRT-2 and base line (K) and ratio of change
56.69 x .616 = 34.921 x (Ratio of change) 1.091=38.098 mm , 8200 RPM for new Engine =39.0625 mm

Hope no one got to big of a headache. As always some one check the math

Adnoh

Thanks again for your help.

I seem to not be able to find pwk39 carbs anywhere not sure if they are made anymore. Pwk38s are around though.

Engine started a couple times. With 50/162 jetting it’s so fat she won’t free-rev very high at all. Backyard smoke cover. I went back to the 145 main for a test and looks like that helped. I need probably a 150/155 to play with. I should get better options in the mail today/tomorrow. Air box and snorkel are there with a k&n filter. Someone drilled the bottom of the air box but the intake looks very restrictive which is why jetting was off with the 162.

When I go Pwk38/39/40 I’ll probably change a few things to get higher airflows like maybe an open filter. Pwk42 is off the table.

Water switch works. Fan Turns on when the radiator reaches 172F.

Compression came up after 20m of runing and two heat cycles on the trailer. It’s at 186psi now.

It’s 100% back together. I got my pyro meter yesterday but it’s broken from China I should have known better.

The carb/airbox/snorkle my be REALLY REALLY restrictive on this thing. I'm now doing some up/down quick road rolling tests and the jetting is WAY way WAY too rich at 50/162. I'm not hammering her out for long - I cant in fact as there a fuel rev limit happening - Plugs are coming out wet as hell. Carb slide is indicating carb is DRENCHING the motor (( Internal Combustion Engine ? )) with fuel.

Idle circuit - The 50 pilot seems too big. I dropped it to 48 and seems now I can get a better idle ** I may increase this back to a 50 - just a sec.

The needle (J35A) is also too rich in conjunction with the main jet (162). I dropped the needle to lean it out still with the 162 and it wasn't enough. I switched to a R1370N needle - which is longer than the J35A - follows the same exact contour but the added length (L1) adds a smaller point down longer/lower into the bowl by 4.5MM. It too wants to be at the lean setting.

So I started dropping the main jet - 162 -> 155 helps slightly, but the Engine still won't rev out much above 6,000rpm. Leaves a spyhunter smoke-screen still.

I didn't want to, but I didn't have anything between 147-152, so I dropped from a 155 -> 145 because that is what I had. The 145 main jet woke up the pilot a bit, and so I raised the needle back to middle position. When I did this, the bottom end liked it, but then once again the top throttle was laying down "spyhunter" smoke as before.

So I went ONE MORE STEP - 145 -> 140 main jet. So, that's a full ~20 points leaner than what you recommended, Adnoh. The 140 seems to be performing best - Less smoke and more precise. I'm able to run and have some fun. Even the idle tightened up to where the air screw and throttle stop really started responding correctly. This is a high indication the carb is too small and suction must be way too high - that is the main jet is affecting idle - hence I may got back up to a 50 pilot.

I'm thinking there must be too much suction and restriction from the stock intake that this carb is just... well, needs to be swapped to a 38/39.

It seems like I am on the right track, but does anyone think this is way too lean at 48/140 with a R1370N needle? Before rebuild the spark plug was coming out pig rich black with 50/J35A/145 jetting.

Zero, I say give it what it ask for.
Just for conversation, did you do any thing with the dual intake set up like remove lid and run open box with one clean air filter.
I touched in primary CR, it may help if you add a spacer to the Reed block. Rember just discussing at this point.
Also still have eight in? The seven will put more heat in the combustion chamber for the rich fuel load.
Just tossing out ideas to consider.
Short story, when I first built an ody back in the day I started leaning things out to discover it was an air issue. Basicly not enough. Had some CO Pistons.
It's still tight so foul a plug or two read the plug and see what it telling you.
It's not normal to me to be experiencing your issue , unless it's a CDI (Capacitor Discharge Ignition) thing. I chased my tail for two weeks with one that acted that way. We had 120 in it and still no luck and I said no way in hell.

So based on air pump un cork it first. Then work on it and then you can go back to air flow though filters.
That is what I would do first. I'm a believer in giving it as much air s it can handle. Untill you get pipe temp it will run fat on bottom. Product of port timing. Hit about six inches from manifold with a heat gun and in the center of the belly. To get an idea of wave timing. That of course once it hits off the bottom. Run it in the middle and use over rich past 3/4 to control.
This is why I remove main to start. To get off idol to half hit then install and step it up from there.
Great inform on stock carb settings valuable information.
Crank pressure still around 185?

As Always each is it's own animal. So what work for one is not always for others.
Im sure I read you reset float height. Any coming out over flow tube? I always check it for dirt sticking or leaking.

Not sure what you mean by dual intake filters. On this pilot:

From the back of the carb - stock 90degree elbow connecting to the stock airbox. Airbox lid is on, as well as a 24"+ snorkel which picks up air near the tail light. The bottom of the airbox was also drilled with what looks like about a dozen or so 1/2" holes and so air gets in that way as well.

There is just one big air filter inside the airbox. Its a K&N aftermarket filter - looks like one of their universal cone filters. I cleaned it really well, and then just lightly sprayed a tiny bit of oil on it. It hose-clamps to a receiving end inside the air box. There are no other 'filters' or restrictions I can tell - other than the snorkel (Which probably makes zero sense given the airbox is drilled!)

My plan is - when I move to a larger carb - to open it up immensely - maybe even a completely open filter to atmosphere, with some mud guards or something. Maybe even attach a UMI filter straight to the carb itself - 10 inches long and protected with a splash gaurd. i don't intend to submerse this pilot more than a few inches.

I guess I could pop the top off the air box for testing.

I'm getting a good Pyrometer installed today also.

Still running a BR9ES plug atm - because I cant get a decent read on if its too cold. I may try an 8.

Yup compression is still at 186psi

If I'm following you right.

First plug chop

BR7ES

And so it’s time to increase jetting and run a br8es

Can we assume it's cleaning out now.
I agree way lean. Also keep eye on plug temp. It too hot now however may change once you get it closer 2 mm the combo of both would be my choice. Loook forward to the rest.
Thank you posting all info. It makes it easy to follow along each step of the way. On next plug chop can you post gap number as well.

I’m back up to 48/150 jetting and will try and get another plug chop today. The br8es plug is indicating correct heat but the issue is I’m all out of new plugs for doing plug chops and don’t want to risk w a br7. Did run a warm compression test and pushed 176 psi. Then later it was back to 180 cold. Mid throttle seems to load up slightly on the 1370 needle middle clip, but then it pulls great in the mid. Great indication Main was lean at 145. Hard to explain but definitely wants more fuel up top as she flattens out with not much more go after 3/4 throttle which could also be contributed to the small carb.

Guages are indicating peak rpm of 7200 and pyrometer isn’t getting over 1100F.

After the day and Engine cold noticed the overflow bottle was more full than beginning of day, and the radiator was 1/2” low. I think the radiator cap may not be sealing well and letting air in instead of pulling back on the overflow. I ordered a new cap found a forum member who had one.

I met a group of hardcore UTV drivers/racers and got a ride with a pro. Definitely a diffferent world for sure! Those guys are nuts! I was sent into orbit lol!