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  #1  
Old 06-07-2011, 10:44 PM
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Default Full throttle Bogging down..

Derbi gpr 50r
At half throttle the bike is fine. At full throttle the bike boggs down, very fast. I messed up by tinkering with the air/fuel screw. Please help!
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Old 06-07-2011, 11:29 PM
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turn the air screw in fully then turn it out 1.5-2 turns (whichever it runs better at) did it bog after you messed with the air screw or before? if it was before then you need to set your floats.
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Old 06-08-2011, 07:56 AM
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The air screw has nothing to do with full throttle. The air screw alters the pilot jetting and needle - not the main jet.

Clean your air filter. If that doesn't do it, you might look into cleaning the carb and if that fails, you are likely looking at changing your main jet. There's not enough info in your post to make any further reccommendations.


What kind of bike is this? Never heard of a Derbi.

Scott
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Old 06-08-2011, 12:32 PM
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you shouldnt notice too much on top by playing with the air screw. shouldnt is kind of an objective statement though. as soon as your engine is turning over, vacuum is trying to draw fuel through the low speed circuit of the carburetor. it continues as long as there is a vacuum, and air moving over the exposed orrifices. so it CAN affect the high speed operation as well as the rest of the rpm range. For it to make your bike do as you describe, it sounds like yours would have to have been very close to bogging under the conditions mentioned, as the low speed circuit has such a small affect on the high end operation.

---------- Post added at 05:32 PM ---------- Previous post was at 05:31 PM ----------

mx, you must have never read dirtbike or mx action in the 70's and 80's if you missed the "Derbi".
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Old 06-08-2011, 02:22 PM
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Quote:
Originally Posted by cm517chris View Post
Derbi gpr 50r
At half throttle the bike is fine. At full throttle the bike boggs down, very fast. I messed up by tinkering with the air/fuel screw. Please help!
Weren't you asking about jetting for a new pipe on this bike awhile back?
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Old 06-08-2011, 02:26 PM
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Quote:
Originally Posted by ossagp View Post
mx, you must have never read dirtbike or mx action in the 70's and 80's if you missed the "Derbi".
I don't know how to read...

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Old 06-08-2011, 03:22 PM
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Quote:
Originally Posted by MXtras View Post
I don't know how to read...

nawt evereewon kan tipe eether
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Old 06-09-2011, 02:32 AM
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Thanks for the help all!
I turned in the air/fuel screw all the way, then turned it out 1.5, and fixed the idle screw. It runs perfect after cleaning out the carb as well. I also put back on the stock exhaust, as it ran just fine with that on. But I now have a full Arrow Exhaust system practically brand new if anyone wants to buy.
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again thanks for the help, much appreciated!!
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Old 06-09-2011, 09:03 AM
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If you changed pipes you may have experienced a really lean condition. If it felt like it just "died" and stays dead as long as the throttle is held wide open, you may have done just as I described. People that used to take the baffles out of their exhaust pipes had that happen frequently.

If after holding it open a couple of seconds and rolling back slightly on the throttle it acts like the engine restarted, then that is likely what happened.
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Old 06-09-2011, 09:55 AM
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Quote:
Originally Posted by cm517chris View Post
Thanks for the help all!
I turned in the air/fuel screw all the way, then turned it out 1.5, and fixed the idle screw. It runs perfect after cleaning out the carb as well. I also put back on the stock exhaust, as it ran just fine with that on. But I now have a full Arrow Exhaust system practically brand new if anyone wants to buy.
Email -- [Only registered and activated users can see links. ]
again thanks for the help, much appreciated!!
Do I detect a smiggin of sarcasm?


Really if you wanted to run the new exhaust for the added performance then contact the manufacturer and ask about suggested jetting.
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Old 06-11-2011, 03:40 PM
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Quote:
Originally Posted by MXtras View Post
The air screw has nothing to do with full throttle. The air screw alters the pilot jetting and needle - not the main jet.

Clean your air filter. If that doesn't do it, you might look into cleaning the carb and if that fails, you are likely looking at changing your main jet. There's not enough info in your post to make any further reccommendations.


What kind of bike is this? Never heard of a Derbi.

Scott
It's a Derbi gpr 50R 2003. Nice little bike goes pretty fast stock.
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Old 06-13-2011, 07:45 AM
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What kind of bike is this? Never heard of a Derbi.

Scott
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Old 06-16-2011, 11:31 AM
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We've had tremendous changes in weather here in NC and my bikes blubber on top when it gets hot.
That's a sign they need to be rejetted, they're too rich on top.
Just last week temps were in the 92-97 range and bikes that ran perfect at Diamond Dons in Texas last month were blubbering in the blistering humid temps here in NC.
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