85cc kit from Scootertronics install PLZ HELP!!

[Kenho21]

Haven't been on this forum or my scooter for two years now  but hoping to get back on the road very soon. I bought an 85cc Kit from Scootertronics 2 years ago, installed it and it made some god awful loud ticking noise me or any of my friends cannot figure out. It's not metal on metal contact inside the piston as far as any of us can tell, but I cannot figure out what it is!?!?

Has anyone here installed this kit or had the same problem in any other way otherwise? I also installed a larger racing camshaft hoping that would solve the problem but still no resolve...

[mono]

Can you post a recording of the sound somewhere ?

[sidthesloth]

Valves hitting piston, piston skirts touching crank?

[Kenho21]

Sidthesloth: I've talked about it with a few different people and they've said the same thing. I clayed the top of the piston and saw no contact anywhere and looked at the bottom very closely and still found nothing...  those were my first thoughts too. The funny thing is I work at a service department of a car dealership, just too bad they fix Chevy's not Kymcos. Any other thoughts?

Mono: It's been put up for almost two years now and its killing me. I'm going to take it out this weekend and start toolin around with it again but haven't done so yet. As soon as I get the old fuel out and get it started up I will try to record the sound a post it somewhere. It may be hard to hear on a recording but it's worth a shot. It is definitely a loud tick, like metal hitting metal.

Someone mentioned it possibly being the wrong octane fuel which seems far fetched to me or another suggestion was the piston arm is loose around the thing it holds on to(sorry can't remember the name).

[sidthesloth]

These scooter engines are very compact, one noise can echo through and sound like coming from somewhere else. Before stripping the engine again, go through and have a look at the variatorto make sure it is not rattling, also look at your generator, make sure nothing is loose, no small stone or bolt is in there rattling around. Maybe a cracked piston?
Only suggestions, hope it is something simple like that.

[Kenho21]

Thanks a lot for the help all! I will definitely heed your advice as I start my project soon and will let you know what happens!

[mono]

It could also be plain old detonation because of a higher compression ratio, in which case you won't find any mechanical cause. (only some serious damage after running the engine for longer than a few seconds or minutes)

Did the kit come with a larger cylinder head or was the kit explicitly specified to be used with the standard 50cc cylinder head ?


BTW, if detonation is indeed the cause, old gasoline and a racing camshaft can make things even worse.

[Kenho21]

Detonation was one of the things I checked for as well. I believe the noise would usually change when its at idle and when I applied some throttle, but it didn't. So I'm still at a loss... what about slack between the piston arm and the crankshaft?

[mono]

Detonation at idle (throttle closed) is almost impossible, unless the compression ratio is _very_ extreme.

Slack/play in crankshaft bearings could be the cause, but it would have to be very large (or otherwise the clearance between the valves and piston top or at the edges of the piston would have to be very small) and you would probably have noticed this before fitting the larger kit.

Did you re-check the valve clearance, not only after you fitted another camshaft but also after running the engine ? (the adjusting nut can get loose quite quickly sometimes)

[sidthesloth]

Cam chain slack, guide not in place correctly?

[Kenho21]

Mono: I did check the valve clearance and it they were perfect, I only added the camshaft after I heard the noise in an attempt to fix it. By now you're probably starting to get an idea of my frustration. I'm going to go over this post again this weekend though and use it as a checklist. Let me know if you think of any other possibilities that might be kind of off the wall

sidthesloth: Also checked chain slack and guide...

[mono]

Just some other possibilities :

When you clayed the piston, did you turn the crankshaft for at least two full rotations in order to have both valves stick into the clay, not just a single one ?

Did you also put clay at the edges of the piston to measure the "squish clearance" ?

And before doing these checks, did you _really_ tighten the nuts holding the camshaft and cylinder head, to seat everything properly and flatten both gaskets the same way as they are now ?

Are you sure you installed the cam chain at exactly the right position and, more specifically, the _same_ position on the camshaft gear when you checked with clay on the piston _and_ after checking ?

[Kenho21]

I had a firend helping me that knew more about tearing motors apart and rebuilding them than me, and I believe we checked all of that stuff together, but it was two years ago now so it's har to recall. At any rate I'm am going to take this whole convo into account this weekend when I get back at it and will definitely let you guys know what happens and probably have a few more questions. hahaha Thanks for everything so far