08 has low power and will not rev past 10k

[Donnyd21]

I bought a 08 that was knocking, it would drive ok still, noticed on the old engine that it would not rev past 10k and was low on HP, I got another 08 engine, completly took apart the carbs, cleaned them (went through 2 cans of carb cleaner), blew out with air, set the idle screws to 2.5 turns out and put it back together. New motor is doing the exact same thing, low power and wont rev past 10k, it WILL start right up and even idle perfect at 1100 RPMS, I did verify valve clearance and it was good, also cam timing is spot on, gas is new, new plugs, sliders on carbs move up and down like they are supposed to, both cyls are firing verified by touching exhaust, stock airbox and a MusArri slip on exhaust without the baffle (super loud), stock carb jetting, I really do not think having a slip on would cause the massive power loss and brick wall at 10k rpms but I could be wrong. I do have a stock muffler coming it will be here friday. Also the timing chain is very noisy from 6k-9k. Any ideas? Its NOT the driveline, tire spins freely and brake calipers are not stuck. Im trying to sell this bike soon and this is killing me, may have to get another engine due to the noise too.

[Alex]

Jetting could be way off. Even many stock bikes with stock exhaust have fueling issues that jetting can account for. The idle screws / idle knob setting won't matter for this high-rpm bogging. Is the airbox/snorkel clear? A clog there could cause exactly what you are seeing, as that would be when the highest airflow would be necessary. (similar thread here)

[Donnyd21]

Originally Posted by Alex

Jetting could be way off. Even many stock bikes with stock exhaust have fueling issues that jetting can account for. The idle screws / idle knob setting won't matter for this high-rpm bogging. Is the airbox/snorkel clear? A clog there could cause exactly what you are seeing, as that would be when the highest airflow would be necessary. (similar thread here)

I dont think the guy who bought the bike new in 08 would have kept it very long if it had factory jetting issues, the airbox is clear, I even took the side cover off to allow more air in and still has same issue....even adding choke while riding does nothing for it

[Alex]

That's interesting re: the choke; may be worth checking into whether it is working at all.

[cuong-nutz]

Did you verify that the floats move freely, height correct, and that the float valves are not hanging up on something? Also, did you check that the needle jets (the tube body that the main jet screws into) is clog free? I think there are two small side holes on the body that helps with aerosolization of of the fuel when it's sucked up into the carb body. I can't remember if that was for the pilot jets or both.

Seems to me it's a fueling/jetting/carb issue.

Your idle jets control idie, needle taper controls mid range and mains are top end/WOT.

[Donnyd21]

Originally Posted by Alex

That's interesting re: the choke; may be worth checking into whether it is working at all.

Choke def works, I use it to start the bike when cold

Originally Posted by cuong-nutz

Did you verify that the floats move freely, height correct, and that the float valves are not hanging up on something? Also, did you check that the needle jets (the tube body that the main jet screws into) is clog free? I think there are two small side holes on the body that helps with aerosolization of of the fuel when it's sucked up into the carb body. I can't remember if that was for the pilot jets or both.

Seems to me it's a fueling/jetting/carb issue.

Your idle jets control idie, needle taper controls mid range and mains are top end/WOT.

Yea all the holes are clear, even the tiny ones at the bottom of the throttle blade, verified there was carb cleaner coming out when spraying it through the main jet. Emulsion tube is completly clear too. Needles were replaced with new ones when I rebuilt the carbs, float height is spot on.

[cuong-nutz]

Can you rev past 10k in neutral?

You can watch the carb bowls fuel when you rev the bike when you hook up a clear hose/tubing to the bowl drains and compare it to the carb body.

[Donnyd21]

Originally Posted by cuong-nutz

Can you rev past 10k in neutral?

You can watch the carb bowls fuel when you rev the bike when you hook up a clear hose/tubing to the bowl drains and compare it to the carb body.

Sure cant, does the same thing under a load or not. I am starting to guess if i have the correct jets or not, anyone have a pic of the stock jets numbers? I recall seeing a 100 faintly on the main jet today while cleaning, I could not see anything on the pilot jet tho

[cuong-nutz]

Stock pilots are 38s and mains are 98s


Stock data sheet per FSM:

Main Jet #98
Optional Main Jet #92, 95, 100, 102
Main Air Jet #100
Jet Needle #L: N9VU, #R: N9VW
Needle Jet #6
Pilot Jet #38
Pilot Air Jet #100
Starter Jet #48
Pilot Screw (turns out) #L: 2 1/2, #R: 1 3/4
Throttle Valve 11° 00’
Idle Speed 1 300 ±50 r/min (rpm)
Carburetor Synchronization Vacuum Less than 2.7 kPa (2 cmHg) difference between two
carburetors.
Service Fuel Level 0.5 ±1 mm (0.02 ±0.04 in.) above the mating surface of
carburetor float bowl.
Float Height 17 ±2 mm (0.67 ±0.08 in.)

[Donnyd21]

Well then maybe he did do a jet kit, I know my needles have 6 slots in them to move the clip up and down to adjust the height so I dont know if those are stock or not.