September 17th, 2014, 03:16 PM | #1 |
ninjette.org member
Name: Donny
Location: Oklahoma City
Join Date: Jun 2011 Motorcycle(s): 2008 250R Posts: 36
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08 has low power and will not rev past 10k
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.
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September 17th, 2014, 03:38 PM | #2 |
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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)
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September 17th, 2014, 03:43 PM | #3 | |
ninjette.org member
Name: Donny
Location: Oklahoma City
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Quote:
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September 17th, 2014, 04:11 PM | #4 |
ninjette.org dude
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That's interesting re: the choke; may be worth checking into whether it is working at all.
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September 17th, 2014, 05:26 PM | #5 |
RIP Alex
Name: Cuong
Location: Houston, TX
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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.
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September 17th, 2014, 05:31 PM | #6 | ||
ninjette.org member
Name: Donny
Location: Oklahoma City
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Quote:
Quote:
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September 17th, 2014, 05:40 PM | #7 |
RIP Alex
Name: Cuong
Location: Houston, TX
Join Date: Apr 2011 Motorcycle(s): '10 250r, '09 265r Posts: A lot.
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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.
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September 17th, 2014, 05:58 PM | #8 |
ninjette.org member
Name: Donny
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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
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September 17th, 2014, 06:04 PM | #9 |
RIP Alex
Name: Cuong
Location: Houston, TX
Join Date: Apr 2011 Motorcycle(s): '10 250r, '09 265r Posts: A lot.
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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.)
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September 17th, 2014, 06:11 PM | #10 |
ninjette.org member
Name: Donny
Location: Oklahoma City
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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.
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