Low power, Brand new Engines?

[crassius]

agree, I'd try leaner - you need a hanger on that muffler too

 

[Jason Kotchey]

Just a quick note to what I found and what I did to fix the problem. Sorry it took so long to remedy the issue, but I appreciate all the input from you guys! Ultimately I changed the cylinder sleeve. I had another engine that broke it's mounting studs off, so I took that cylinder head and sleeve off and put it on the silver block. I did notice on the down stroke the intake holes on the left and right sides of the piston(I can't remember the proper definition), were so much more exposed with the new sleeve. It is a 40 mm intake on the sleeve I put on the block.

 

[crassius]

those are called the transfer ports - factory must have put wrong one on that motor (or they weren't machined out properly) - that's one of the reasons I take motor apart for inspection before selling a kit

 

[FNTPuck]

I'm surprised just the cylinder made such a difference, I would have bet money(and lost) that it was the piston or rings. Like crassius said it must have been a defective cylinder.

I had a motor that behaved almost exactly like this, and when I tore it down the piston arrow was wrong so the locating pins were on the wrong side. Flipped the piston and compression went from ~65psi to 150psi and performance was normal.

 

[Jason Kotchey]

My second sleeve came in and I took a pair of pictures to show the difference in the transfer port opening (different blocks but, it is the cylinder were looking at). I don't know why they are different but they are noticeably different! Also I noticed that the arrow faces the intake (second photo)? The bike is running great! Hope this helps someone else someday!

 

[Lukesky36]

With my experience a open O exhaust port and a shaved piston skirt or one that already clears on TDC full intake clearance goes along way to knowing you have a good motor.

 

[Street Ryderz]

My second sleeve came in and I took a pair of pictures to show the difference in the transfer port opening (different blocks but, it is the cylinder were looking at). I don't know why they are different but they are noticeably different! Also I noticed that the arrow faces the intake (second photo)? The bike is running great! Hope this helps someone else someday!

This isn't really the issue as having less of that transfer open just means the velocity at open has to be high.Did you notice the huge difference in blow down duration though? That's what's making the difference in performance.