Pcx Yuminashi Chainsaw 164!

[Valeriy7]

good..I'm so sorry about all this about the war... soon you can ride a motorcycle again.... I'm so far away and so scared,,..I don't know how you guys are so strong and put up with it....., ,..a lot of strength...

Thanks a lot!

[power-full]

Hello . why don't they mount the yuminashi turbine with more cooling blades?
until seeing me it has worked

[Pcxdemon]

Hello . why don't they mount the yuminashi turbine with more cooling blades?
until seeing me it has worked

Blades are orientated counter to stock. Orginal fan pulls air in thru the radiator, what is that one going to do?
I tried that one on mine few years back, and my temperature gauge went up...so, ive went back to stock fan. Works well.
Although, I have bought am electric fan, so I can ditch the power sapping mechanical one away. May gain extra 1hp..I hope...

[Hobbit112]

Pcxdemon, you ever Dyno your set up?

[Hobbit112]

A question on throttle body and manifold size for the Yumanishi 150cc head. Which size would be best? I am seeing 30mm, 32mm, and 34mm throttle bodies and corresponding manifolds. I know the intake valve is 29mm and I do know that going too large can be a detriment.

Insites? Suggestions? I haven't made a decision yet but probably will need to do so soon.

[power-full]

32mm our best 35mm

[power-full]

32mm our best 34mm
My 34mm forza ...
https://youtube.com/shorts/_U4cts3kxfk?feature=share

[Hobbit112]

Thanks for the feedback power-full. We have a brand here in the Philippines called Pitsbike which has 30, 32 and 34mm throttle body and manifold sets for about $60 US including local shipping. I don't know how good they are but might be worth trying.

Screenshot_2022-05-27-19-10-33-03_2abacf34316c15a12c3cebabd203d65f.jpg (90.77 KiB) Viewed 961985 times

[Pcxdemon]

Pcxdemon, you ever Dyno your set up?

I did while ago. It had 31mm throttle body and ok transmition set up. Then again, had no base, stock pcx to test and compare first so I guess dyno calibration may have been incorrect. Anyway, it put out 15 something HP at the wheel. Once I installed 34mm Forza throttle body and dialed in transmition better, it became much more...but never went back for retest..

[Pcxdemon]

A question on throttle body and manifold size for the Yumanishi 150cc head. Which size would be best? I am seeing 30mm, 32mm, and 34mm throttle bodies and corresponding manifolds. I know the intake valve is 29mm and I do know that going too large can be a detriment.

Insites? Suggestions? I haven't made a decision yet but probably will need to do so soon.

34mm TB all the way...even better if you could install 31mm intake valve...I haven't done the valve,would love to. That's my restriction now, and I can feel it...

[Hobbit112]

Went with the 32mm Pitsbike set up for now which should be plenty with the 29mm valve in the 150 head.

Have received all parts now so install should be next week. Mechanic is going to modify my exhaust for the bore kit (don't know what will be done yet) and install a plug for an AFR probe. Mechanic asked if I want it tuned but don't know how much can be done with stock ecu other than a reset. Will run it on the Dyno so have my fingers crossed.

[Hobbit112]

Installation complete, now time for break-in. Having an issue with cold starting. Could turn motor over once, then nothing. And with new LiFePO battery with 180cca. Turned crank over manually a few times with a wrench and then would start. Hoping for better tomorrow.

[Hobbit112]

Cold start issue has resolved itself, rings just needed to seat. Also had an overheating/coolant leak problem which we tracked down to the bore deck not being even. A slight sanding and now good.

Back to breaking it in. Have about 100km run AFTER fixing the deck, about 250km total. Oil change today.

QUESTION:. At certain rpms runs rich. Using stock ECU and a 180cc 10 hole injector. Will the ECU learn to decrease fuel at those rpms? As I said, only have about 100km on the final fix.

[Pcxdemon]

It will run rich on low throttle, half to 3/4 throttle should be around 14.7 and full throttle is at 13.2afr.

But that's on mine with takegawa fuel corrector.
Im not sure regarding your question on self correction. You need an afr meter and just watch what's it doing...

[Hobbit112]

Have installed a 170cc injector with improvements notes. At least it idles now, lol. Still experiencing surging/sudden richness at various rpms. Mechanic adjusted something and I did notice some improvement there also but more is needed.

[Hobbit112]

UPDATE:. 2000 km refresh. No longer idles, keeps searching to lower rpms until it dies, this is when fully warmed up. Tries to search down to 750-800 rpm, stock is about 1500. @ 1000 it will keep ticking over. Have also developed an oil leak, looks to be coming from the head at the bottom slot of the timing chain. Coolant leak at the head seems fixed, no overheat issues. Going to install a slightly hotter sparkplug, the 9 series.

FYI my mileage is running around 36 kilometers per liter, when stock was around 52.

[Hobbit112]

Installed Yuminashi full set of 164cc. I put a long gear 15/45. Started driving. In a few days I drove 180 km. Then the scooter started overheating. The red light came on. I pumped the water system many times, the result is deplorable. The steam is collected, the pressure in the radiator, the liquid is sent to the expansion tank. It does not return when the engine is cold. I changed the thermostat, checked the pipes, hoses, pump seal. No air leaks found. Could it be the head gasket?

by the symptoms the joint must be gone !!
I almost bet you are using the original 1.1 bar radiator cap!!! if this is one of the problems, another cause could be injection.. lack of gasoline causes overheating / engine clogging

If the joint is gone then is a new radiator needed?

[Valeriy7]

Installed Yuminashi full set of 164cc. I put a long gear 15/45. Started driving. In a few days I drove 180 km. Then the scooter started overheating. The red light came on. I pumped the water system many times, the result is deplorable. The steam is collected, the pressure in the radiator, the liquid is sent to the expansion tank. It does not return when the engine is cold. I changed the thermostat, checked the pipes, hoses, pump seal. No air leaks found. Could it be the head gasket?

Problem solved. The cylinder head and cylinder were not flat. Aligned. I went back to the TAKEGAWA 170cc because it had a new gasket. I put a three-layer gasket, I did not dare to use a single-layer one. The flight is normal, but more than 104 km / h on GPS does not edit. True, at a temperature of +8 on the street. Cut-off at 127 km / h. In the kit I still have a 1.6 bar radiator cap. Injector 170ss. Throttle 31 mm. Manifold, air filter hose from Yuminashi, camshaft and rocker arms with double springs from Yuminashi, FI CON2 Takekawa. NGK9 spark plug, Yuminashi CVT and 15/45 long gear. The question is, can Yuminashi's copper head gasket be reused if made soft?

[Hobbit112]

Installed Yuminashi full set of 164cc. I put a long gear 15/45. Started driving. In a few days I drove 180 km. Then the scooter started overheating. The red light came on. I pumped the water system many times, the result is deplorable. The steam is collected, the pressure in the radiator, the liquid is sent to the expansion tank. It does not return when the engine is cold. I changed the thermostat, checked the pipes, hoses, pump seal. No air leaks found. Could it be the head gasket?

Problem solved. The cylinder head and cylinder were not flat. Aligned. I went back to the TAKEGAWA 170cc because it had a new gasket. I put a three-layer gasket, I did not dare to use a single-layer one. The flight is normal, but more than 104 km / h on GPS does not edit. True, at a temperature of +8 on the street. Cut-off at 127 km / h. In the kit I still have a 1.6 bar radiator cap. Injector 170ss. Throttle 31 mm. Manifold, air filter hose from Yuminashi, camshaft and rocker arms with double springs from Yuminashi, FI CON2 Takekawa. NGK9 spark plug, Yuminashi CVT and 15/45 long gear. The question is, can Yuminashi's copper head gasket be reused if made soft?

Aha! I had a similar experience! Continued to lose coolant (even more than before!) so went to another mechanic. Several new gaskets (oil seals), a new water pump and reset the cylinder head with new stock 150 head gasket and problem corrected.

[power-full]

I have a new kit at home... because my kit already has more than 59 thousand km on it... but before assembling it I'm going to have it rectified as I can already see that Yuminashi fails a lot in this part