Need help with Kinetic moped

Jesus G. saldivar /

I did a compression test on my 2003 kinetic and got only 45 psi. Took the motor out thinking it was the piston and to my surprise nothing wrong. What could it be that is causing the low compression? Another thing that was weird to me is that the cylinder has an extra hole in it as well as the head. I guess somebody was porting it or something. But I had it working for a long time and it was much faster than my Ciao.

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Re: Need help with Kinetic moped

♣Slew Foot♣ /

Leakdown case gasket. They oval around the flywheel on the way out

Re: Need help with Kinetic moped

That extra hole is for a decomp valve. It's all standard Vespa stuff

Did you have the throttle fully open when you tested it? Spun it over with a drill? I bet on your tester reading low

Re: Need help with Kinetic moped

Jesus G. saldivar /

I did have the throttle all wide open while pedaling the kinetic and got only 45 psi and I did it twice just to make sure. The bottom gasket, the one between the cylinder and the crankcase fell in pieces when I removed the cylinder. I guess Slew Foot is in the right path. Can I just make this gasket out of gasket paper? Regards and thank you for the feedback!!!.

Re: Need help with Kinetic moped

Shouldn't use gasket paper it's too thin usually, but I'm sure it can be made to work. I make mine out of thin cardboard, like from a cereal or saltine cracker box. What ever you choose to use, soak it in two stroke oil before installing.

Re: Need help with Kinetic moped

Dirty30 Dillon /

Gasket paper works great for base gasket, especially given Vespa/kinetic originally only used a tin gasket.

I'm surprised that you've got 2 vespa-based bikes and never knew about decompression.

Could be stuck compression, or worn rings. What is your ring gap?

Re: Need help with Kinetic moped

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> Gasket paper works great for base gasket, especially given Vespa/kinetic

> originally only used a tin gasket.

>

> I'm surprised that you've got 2 vespa-based bikes and never knew about

> decompression.

>

> Could be stuck compression, or worn rings. What is your ring gap?

I'm betting on improperly seated decompression valve.

Re: Need help with Kinetic moped

Jesus G. saldivar /

I know theorically of the decompression valve being there for the starting of the moped since it can help you getting some momentum thus making the pedaling a little bit easier. Also, in case you need to turn off the engine in case of an accident or before crashing. It will make the engine lose compression and thus turn off. However, physically to see an extra hole in there for me was kind of weird. But now, thinking about it, that hole makes the air to travel out of the engine all the way from down there, creating like a vacuum and turning off the engine. Unless you think different, let me now if I am wrong. Another thing is that I always look to fix all the easy, common things first. No compression, one thinks of rings, pistons, or cylinder, the top end of the engine. Other thing is weird for me is that people tend to be to exaggerated with respect to mopeds. I have 11 of them and none of them had a broken seal on the bottom end. These things were made to last. When in need of an advice people go for the most difficult part to replace (the seal). I dont know if they do it on purpose, for one to ruin everything or to look for professional help. Anyways, I'm placing a new cylinder jug, crankase made of thick gasket paper before I go down further into the engine. Forgot to mention, that the guy who sold the kinetic to me was a 350 pounder guy and I guess that was also another reason why I thought the piston was stressed out. Regards!!!

Re: Need help with Kinetic moped

♣Slew Foot♣ /

Seals are cake an ovaled case champher isn't. I seen 6 kinetics 3 were clutch 2 were wiring the last one was the totalled bearing cup.

Re: Need help with Kinetic moped

low compression has nothing to do with your one case seal nor your base gasket. Its rings, head to cylinder surface, and decomp seal. and your plug threads.

Re: Need help with Kinetic moped

Dirty30 Dillon /

I'm sure you have case pressure loss along many of your original seals, just tuning around them or letting them be as a stock bike can run a long time with leaking seals and a determined mechanic and rider.

In terms of the Vespa, it is literally one seal and you have replaced every seal in the motor, so it's a good insurance.

And seals were specifically not meant to last. They are a wear part.

Re: Need help with Kinetic moped

todd amundson /

Harbor freight compression tester?

Re: Need help with Kinetic moped

Jesus G. saldivar /

Today I assembled the engine back together putting a new gasket between the cylinder and the crankcase. I used a thick one, applying a bit of red gasket maker on both sides of the gasket. I torqued it to 10 pounds and cleaned everything super nice with brake cleaner. Tomorrow is going back. Wanted to let. you know that I blew air through the intake with my mouth and the air does not go anywhere, meaning I guess, that the inner seal is still holding. I also convinced myself that somebody ported or did something on this bike to make it faster, the rod that moves the piston has a lot of steel removed on purpose. No wonder why this thing is much faster than my Ciao. Regards!!!

Re: Need help with Kinetic moped

> Jesus G. saldivar Wrote:

> -------------------------------------------------------

> the rod that moves the piston has a lot of steel removed on purpose.

Post a pic of that rod , please .

Re: Need help with Kinetic moped

Dirty30 Dillon /

> Jesus G. saldivar Wrote:

> -------------------------------------------------------

> Wanted to let. you know that I blew air through the intake with my

> mouth and the air does not go anywhere, meaning I guess, that the inner

> seal is still holding.

This literally tests nothing, except your taste buds for dirty old gas.

> I also convinced myself that somebody ported or

> did something on this bike to make it faster, the rod that moves the

> piston has a lot of steel removed on purpose. No wonder why this thing

> is much faster than my Ciao. Regards!!!

It's not ported. The cranks on the kinetics were sloppily ground from the factory to clearance them. The reason it's faster is because the Kinetics have better stock porting than the slower US ciaos.

Re: Need help with Kinetic moped

Jesus G. saldivar /

I finally had the chance to try my kinetic. All I did was to install a new base gasket using gasket paper and coating it with a dab of gasket maker on both sides. First kick and it started right up. The compression seems to be still low just by feeling the power on the engine while driving it. I cleaned everything super nice in the whole moped but still having the low compression. Tomorrow I am going to do another compression test, just to see if there is a difference. Another weird thing is that is leaking lots of gas through the exhaust. I noticed this while pedaling to start it. The gas was being expelled all the way back through the exhaust like if the carb is directly connected through the exhaust. I tried to put my hand in the exhaust hole and my hand got all wet from the gas. The weird thing is that I was revving it and still working. I even cruised around the neighborhood until the leaking stopped. Any ideas why this is happening? Regards!!!.

Re: Need help with Kinetic moped

If it cleared up after some riding it was probably just gas in the exhaust from previous attempts to start the bike.

Re: Need help with Kinetic moped

Dirty30 Dillon /

Your exhaust was probably flooded with gas from you trying to start it with a base leak.

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