54B looses power at mid to high speed By rcq78 (Read 2,305 times)

[rcq78]

I have a 2008 54B that looses power at mid to high speeds,but don't stall...It will loose it for 10-20 seconds the take back off & do it again down the road....I have replaced the coil & still the samething...The plug looks like it did the day I installed it...It has about 6000 miles on it...I pulled off the carb & took it apart & cleaned it,adjust the a/f screw out 2 1/2 turns...Cleaned the air filter & still no luck...The valves were adjusted about 2000 miles ago....I have a electronic fuel pump on it & have good flow to carb..I have also replaced the cdi...Please help I'm at a loss....Bob

[Alleyoop]

Check your diaphragm for rips or tiny holes if the rubber is damaged it will not lift the needle out of the main jet all the way because it is looseing pressure.
Alleyoop

[Bashan]

Yes, the diaphragm was the first thing that came to my mind, good recommendation from Alley. The second thing would be the fuel pump. I know you say you're getting good flow but you really can't say what it's doing at speed and if it's cutting out intermittently. I'd check the voltage and connections to the pump but you may need to just swap one out to be sure. I'd go with a relatively less expensive vacuum pump for diagnostic purposes, you may find you actually like it better. Rich

[rcq78]

I'm woundering if it could be the valves,even though they were adjusted 2000 miles ago...

[Alleyoop]

Well you have a couple of things to check, the diaphgram is easy it is right on top just take the two screws off and pull the sucker out and check it. Sometimes they will leak around the center where the rubber is being held in place
Alleyoop

[rcq78]

Well,I pulled the diaphgram out & it looks good....I don't see any thing wrong with it....So,what next....it looses power when you keep it at around 4-5k rpm's..it will stay there for a time but then slowly loose power.....the intake valve makes alot of tapping noise....Is there a chance it could be the plug??

This scoot ran good 3 weeks ago..Then I took it apart to fix bushings on the swing arm & then put it back together & on the first ride it started this....I hate to be a PITA But I hope I can get this thing running right with a little help....Bob

[rcq78]

Well,I think I found the problem...I decided to remove & take carb apart again & I found the main jet atleast 1/2 plug with junk...I took a needle to it & wow what a difference....The first time I had it apart I thought it was suppose to be a small pin hole...once I took the needle to it & blew it out & couldn't believe how bad it was...Thanks for all the help guys...Bob

[Bashan]

Never a PITA Bob and thanks for sharing your solution with everyone, we all learn from others experiences. Odd that it would begin doing that after you worked on the swingarm. It must have jostled some crud loose and it lodged in the jet, go figure. Glad you're back up to speed. Rich

[rcq78]

Well,guess what,it's not fixed...Took it for a ride today & still loses power at 55-65..I took the carb off again & cleaned it & still the same.....Would really like some idea here guys.....I have already replace fuel filter,coil,cleaned air filter, I have good fuel flow from fuel pump.......this is really pissing me off....Bob

[Alleyoop]

Ok, lets diagnose it a little. It sure sounds like a fuel problem. When it does it again BACK OFF THE THROTTLE about 1/4 inch and HOLD IT THERE and see what it does.

A. Does it speed up
B. Does it sputter, bog hesitate and then speed up or just settle down.
Alleyoop

[rcq78]

it falls flat on it's face & then will speed up some of the time...But most of the time you need to pull over then it will regain power & idles just fine it never stalls.... when I pull out the diaphram,if I blow down the center of it,should air come out of a hole thats next to the needle at the the bottom....

[Alleyoop]

Ok, that means it is running RICH.
Did you change the MAIN JET or move the needle or adjusted the Fuel Ratio Screw?
Alleyoop

[rcq78]

Yes I did,after I cleaned the carb I screwed it in all the way & then backed it out 2 1/2 turns....could it maybe be a crack in the airbox?? it ran fine a month ago,then I did some work on the swing arm bushing & the first time riding it,it started doing this....

[Alleyoop]

Well if you have a crack it would mean it is running the OPPOSITE LEAN. But if when this happens you back off the throttle a little and it bogs, or hesitate or sputters then settle down that means it is running to rich. So you can try turning the Fuel Ratio Screw HALF turn Clockwise to 2 turns out only and give that a shot.
Alleyoop

[mike6736]

Al, what hole is he talking about in the diaphram??? Look at the 8:36pm post he made...

Sure sounds like it is running rich

Mike