Engine Trouble Bike wont go faster than 24mph with 36t sprocket

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really sounds like a weak motor, but getting same speed with 36 and 44 is strange - I've seen weak motors that sat a while and the base gasket deteriorated (spraying water in the area will show a change if gasket is bad)

without compression test or search for any air leaks , I might try a 41 sprocket to see if that is also same speed

if I had it, I might just throw a new motor in and save old one for parts
 
Even if a wee bit lean up top that would just make a little more power...only the main jet is working at WOT if im not mistaken...So although other adjustments may be needed its not going to effect top end which is rather weak.

Maybe a really dirty air filter?

Only 25mph with a stock pipe?...i wouldve thought more capable than that from what ive seen on youtube.

If its not compression or jetting, i dont know.

Bad CDI box not advancing like it should?
 
Even if a wee bit lean up top that would just make a little more power...only the main jet is working at WOT if im not mistaken...So although other adjustments may be needed its not going to effect top end which is rather weak.

Maybe a really dirty air filter?

Only 25mph with a stock pipe?...i wouldve thought more capable than that from what ive seen on youtube.

If its not compression or jetting, i dont know.

Bad CDI box not advancing like it should?
The main jet does only affect wot but the carb can be rich at idle then lean on the needle and just flat on top but really we dont know because he's not getting to the top end probably best to do as Crassius said and put the stock gear back on and see if it can be dailed in first before trying to get more out of it.
 
You could be right brother it's just deceiving in the pic with oil around the base of insulator and the threaded edge those carb's do tend to be pretty fat on the bottom witch would read like that then the whole insulator being coloured like that makes me think it's set up lean in the middle on the needle.
I'll go back through the thread, but I think he said something about running a performance carb.. Probably the dell. clone so no needle. They in my encounters tend to run richer than NT's. I would like to say go 68 then 66 if needed, but what I would really say is dump it and go back to the NT. He also said it's a used engine so maybe it's not getting a good seal at the crank. Not bad enough to rev. just enough to make it hard to tune.
 
I'll go back through the thread, but I think he said something about running a performance carb.. Probably the dell. clone so no needle. They in my encounters tend to run richer than NT's. I would like to say go 68 then 66 if needed, but what I would really say is dump it and go back to the NT. He also said it's a used engine so maybe it's not getting a good seal at the crank. Not bad enough to rev. just enough to make it hard to tune.
Oh yeah your right!dont know why I was thinking needle it has there so called flat slide lol yeah they do tend to be fat and flat in performance.
 
I was thinking more about the 24mph at WOT and yea its the HP carb which is the dell 15mm clone and he mentioned the exhaust port was worked on and has an oval shape to it...maybe too much back pressure due to the exh. port change with the stock muffler?

Im almost certain though a stock exh with even a stock head can hit 30 plus.
 
Mine looks oily. What does that mean

This might help everyone.
If it's correct that is, it seems pretty close for the right one.
spark-plug-lean-rich-optimal-640x360.jpg

From: https://www.tuningmatters.com/how-tos/beginners-guides/check-spark-plug-correct-carburetor-setting/
 
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