Engine not reaching top end speeds

I got my motor back from my buddy who made a new bracket system for it including larger bolts for it. The problem I'm having now with it is the motor will bogg out and actually slow down alittle when I reach 30-35km. I thought it was the spark plug as it happened to be very loose and I tightened it good and took it out again and same problem. It's bogging out on me and I don't understand why it's being stupid like this. Everything is nice and tight. The spark plug is black on the bottom so I don't know if it's that.. It does run the motor just not what it used to.. The weird thing is that it's not riding rough anymore. Wiring maybe ? I can't see that being the issue. The wiring looks fine to me.

Tomorrow I will test it again as I have replaced the spark plug and I'm letting the carb air filter dry as I washed it really good with hot water. I also used carb cleaner in the carb as well. I did all this after my last test run and have no done gone on another test run yet.

Suggestions ? This is starting to get on my nerves...

goat herder said:

My first guise is the float bowl might not be letting enough fuel in the other guise for a cause is clogged fuel filter. Be careful with the carb cleaner theres no lube value to it washing the oil temporarily off the rings....Also give this thing time to brake in...The stock filters in the tanks are famous for clogging . They will fall apart to . Recommend a in line fuel filter...

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It's broken in. I've had it at 44km before and I ran it all winter start to finish.

I ran it again and I managed to maybe squeeze an extra couple Km of speed. It's still bogging but not as bad.. It's like there is something preventing it from going a certain speed.

- Bad mix ?

- The clip is to low or to high and it's not getting enough gas ?

Suggestions ???

I just made a new batch. The gas sat in a Jerry can and the oil still in the bottle. I'm using Castrol 2 stroke oil. I tried playing with the idler while it was running and it has no effect on the engine at all. I have another carb I can try to see if it's the carb. Mix is 20:1 -22:1 In and around that.

Bump!! (filler)

I changed the plug and there was no difference at all. Depending on the direction of the wind I can get up to 35 before the engine just will start bogging and slow down like it's being starved of gas like when run out of gas. I even tried to go down a hill and pedal and it still refused to go faster and the engine would actually slow down.

Spark plug is nice and tight

I moved the clip up so it's 2 notches from top

I don't know what else can be done. It worked fine until my buddy played around with it trying to get a new mounting system he said he even tried welding the engine to the frame but it wouldn't hold.
The only difference I noticed with the c clip moved up and is the engine rpm. I had to adjust the rpm as it revved to high and would make almost like chocking motion as I climbed up in the higher rpms.

I'm starting to wonder if the engine is just cooked now and cannot be saved. Maybe the welding messed up something inside of it ? No matter what I try it refuses to go as fast as it did before I gave it to
my buddy to get the bolt out and make a new bracket system..

Well I put on the carb that came with the engine and when I took it out for spin i noticed I managed to gain maybe 5km out of it before it would start sputtering like it was being starved of fuel.

I opened up my other carb bent the arms down more and maybe that would help ?

Well the Jerry can was in the living room on the floor and there was large window behind it but there was curtains to block most of it out. It did the same thing on the gas/oil mix that was still left in the tank from the previous batch.

Bikeguy Joe said:

I would look for fuel starvation issues from vibration. If you more solidly mounted the engine, it will cause that possibly.

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I dunno it is pretty solid the mounting. I played with the idle screw again on carb and got the rough riding back and it seems to be behaving normal.. I have not let it go full rip to see if it boggs out. Cross my fingers for whatever reason this works.

I fired off a email to Chris Hill in thunderbay and he had this to say:

If your friend tried to weld the engine casing to the frame, or even
attempted to weld brackets to the engine there would be a good chance that
he has heated the crankcasing to the point that he may have burnt up the
gasket that seals the crankcase together. This would also explain the loss
in power as the engine is no longer able to hold the compression. You should
clean off your engine as good as you can, then ride it for awhile and watch
to see if you are getting any oily residue leaking out from anywhere on the
engine...top, bottom, front, or back...could be leaking from anywhere around
it. It may show the leaking area within a few minutes of the engine running,
or it might take a few hours of running. Your friend could have also melted
the seals, or burnt up a bearing depending on where it was on the engine
that he was trying to weld. I'd be betting more on the crankcase gasket
causing your problems though.

The reason why your engine rpm's increased when you changed the fuel-air
setting is due to the engine getting a leaner mixture...it would now be
getting more air than it should which gives an increase in performance, but
also diminishes the amount of necessary lubrication to the engine
components, resulting in a shorter engine life overall. How much shorter
depends on hard it was run like that as well as your fuel/oil mix. Something
similar would be a race engine...they lean them out like that (and do other
mod's) for a race, but they also tear down and rebuild the engine after
every race because it is so hard on the engine.

If your problem turns out to be the crankcase gasket, I can send one to you.
It takes a lot of time, patience, and mechanical know-how to change it out
though as you have to take the entire engine apart to do it. I do mean fully
apart...everything.
It is less expensive to buy a replacement engine than it would be to have
myself or an engine builder do the work because of the amount of time that
it takes. If you want to give it a try, let me know and I can send what
you'll need. An ugly alternative to changing the gasket would be to clean
the engine up really good with a good degreaser around the area that is
leaking and then run a line of "Automotive GOOP" over the area and let it
set for a couple of days to ensure that it has cured. This won't look as
nice, but should seal it up good enough to be ridable.

Please let me know if you find a leak, and if you want the necessary gaskets
to try and fix it.

Cabinfever1977 said:

30-35mph is fine,what are u tring to kill yourself? and never have anybody weld nothing to your engine and dont leave anyone alone with your engine or bike.
you would probally be better off getting another engine for $79-99 then to try and change all the gaskets and bearings and you still probally have problems.
good luck and let us know how its running.

btw anything over 32mph and my bicycle would probably explode lol.
how would anyone like to loose a chain at that speed and lock up your bike and go flying for a mile into a tree or the pavement.or how about if you blew a tire,doesn't sound like fun.

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I'm not from the US. If it was going that fast I wouldn't care. However it's going 35 Kilometers per hour and NOT miles per hour.