My first motorized bike, few issues so far

Datboi

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I've build my first motorized bicycle. I put a 80cc Chinese engine on a mountain bike with no suspensions.

I mostly use it for mountain biking in the hills and off road, so I give the engine quite a beating. Especally the clutch.


I have a few issues, first of all, what are the pros and cons of running a richer gas-oil mixture, I'm currently running 65ml of oil to 1l of gas as I'm breaking the engine in. What would happen if I always run the engine at that ratio even after break in? Can someone give me a run down of pros and cons?



Let's start with the issues I'm having
4 stroking at full throttle (the engine starts 4 stroking when I stay at full throttle for a bit and the engine starts revving high)

Whenever I'm going at low to moderate speed, the engine 4 strokes at low to mid throttle. If I open up the throttle completely it doesn't 4 stroke until it revs really high


The issue is, I've done a plug chop, the spark plug has slightly tan and looks perfect, If I move the clip on the leanest position I'm scared I'll be running the engine too rich! I tested it at full throttle and mid throttle. What should I do?


2nd issue: low power, possibly low compression or bad clutch.

I have issues going up hills, the engine just doesn't have the power, I feel like there is a compression issue, the gasket on the cylinder is a joke, I feel like this engines lose a lot of compression due to those bad seals. How can I test if I have compression without a compression gauge? The engine does have quite a bit of resistente so idk!


3rd issue: very very loud clutch noises at full throttle.

Whenever I gain some speed, the clutch makes a TERRIBILY loud screeching noise, the more speed I pick up at full throttle, the louder the noise, its louder than the engine itself! The noise is that of a very old metal door opening.

I've put f*** ton of grease on the clutch gears on the right side of the engine. But that didn't fix it.

Im not 100 %sure it's the clutch making the noises. But it only happens when the clutch in engaged, at low speeds there is little to no noise, but the more I pick up speed the more noise!


Could it be that the clutch is slipping at high rpm? The adjustor nut is as tight as I can make it while still being able to turn the real wheel with the clutch pulled in.


Also the clutch doesn't seem very good, whenever I'm going up a hill or from a dead stop it's defently not as grabby as I would like it to be! However it might just be that I expect too much from this clutch? Any tips? Thanks guys
 
Make sure you don't have any grease on the clutch pads, if there is, wash it off with some dish soap and brush them with an old tooth brush to get it all off. Rinse with hot water and let dry, or use blow dryer. Check the inside of the clutch cover for any marks, it's not uncommon for the clutch bolt to touch the cover and make some noise.
 
Make sure you don't have any grease on the clutch pads, if there is, wash it off with some dish soap and brush them with an old tooth brush to get it all off. Rinse with hot water and let dry, or use blow dryer. Check the inside of the clutch cover for any marks, it's not uncommon for the clutch bolt to touch the cover and make some noise.
I did,, gave them a good clean with Alchol and a brush too. No luck
Clutch cover has no marks...
 
For one these engine's put out around 1.8HP after break in, so don't expect great amounts of power.

Oil is debated alot but the general consensus is 20:1 for the first tank and 32:1 after, for average conditions and unknown oil being used.

If your four stroking your too rich and moving the needle up will cause it to become more lean. Show us a picture of your plug.

Check @Chainlube post for clutch. Squealing is not good. Even riding the clutch shouldn't create noise.
Is it true that removing the end of the exhaust pipe bolt will increase hp slightly?

20:1? That sounds very lean, the manual calls for 65ml to a liter for the first 500km

Does a richer mixtures have any downsides exepct a very minor power decrease?

I'll take the cylinder apart now to make sure the noise isn't coming from the piston as I've read on a forum.

To me it almost sound like the clutch is slipping when at high rpm, but there is no way to make the clutch any tighter, otherwise it drags...

Don't have a pic if the plug, it's a caramel color so I should be running good... Dunno
 
Yes but not really recommended and it's noisy.

20:1 is quite rich in oil.

Besides the downsides of synthetics decreasing power with too much. Too much of any oil will increase fouling potential and carbon build up. Controversially. Heavy use (16:1-20:1) of castor based oil cause's a minor increase in power according to older literature.

I like the sound of a caramel color plug so that should indicate your well within the ballpark of a great mixture.

Clutch slipping at the top end is characteristic of a heavily loaded engine. Normally experienced after successful power increase or seen by the few that climb hills.

The way to defeat this is tightening the preload spring. The clutch cable holder needs to be I. Flat head inserted into the hole, landing in one of a few notches that will appear and stopping the adjustment nut. This adjustment nut, once held by a flathead, will stay while the shaft turns and tightening the preload pressure by pushing the bike backwards and pushing it forward will loosen it.
Wait, now that you put it that way, it doesn't make that noise even when climbing really stiff hills, only. When on a flat road at full throttle.

I just did a tear down and took the cylinder off to see the piston and the inside, nothing seems to be causing the noise from there. I'm out of idea. I literally checked everything

I've seen that trick on a video, however I broke the screw that screws in the clutch arm to hold the cable, snapped clean off, so I have to figure out a way to get it out of there.... I wanted to do that but I hold it off due to the fact that I would have to address the screw issue too...

I'm guessing tightening the preload would make the clutch harder too right?
 
Datboi 32:1 is ideal mixture, so half of what you're doing right now. Don't confuse oil/fuel mixture with your AFR (air fuel ratio) which determines the plug color. If the plug is tan-ish then the AFR is right.
Are you sure? The engine manual calls for that 65ml to a liter, and there doesn't seem to be a lot of carbon buildup

Yeah I know, however I'm still getting 4stroking,thats why I'm concerned.


Its weird because it only does it when you reach near top rpm and top speed

And at half throttle... It feels rich too at half throttle some times
 
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Damn. That sure looks useful, hopefully I'll find it at the store.

I hope I didn't strip the inside tho. That would sure be a pain in the ass to fix.
Don't worry about if it's stripped or not, just as long as you put a hole through the arm/old screw that the cable will fit through then put one of those cable locks on the outside.
 
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