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bike wont open up under a load

  • Thread starter Thread starter Lockcuff
  • Start date Start date
L

Lockcuff

Guest
hey everyone, just got carbs rebuilt got the carbs fairly well synched at idle, bike revs fine in nuetral, but when i ride it it spits and sputters aroung 5k on the speedo, any help wouild be great, what am i missing on the carbs, i dont have the airfilter in right now either? set all screws to factory settings, got tons of fuel and new plugs
Thanks
Dan
 
Are you sure it's carb related? Is the timing set correctly and if you still run points, are they adjusted, clean and not pitted? Good spark? Just wondering what basic tuning has been covered.
If the bike revs well in neutral but not under load, that's commonly a lack of fuel. What did you do to the carbs? Floats adjusted at? Pilot fuel screw (underneath) and side air screw adjustments? Floatbowl vent tubes clear and no kinks? Stock bike, stock jets?
Did you replace the manifold o-rings while the carbs were off? How are the manifolds themselves? Any difference between cold rpm idle and hot?
Did you service the petcock? All venting clear? Using a fuel filter? Correct fuel line size? How's the vacuum line? Does the bike run better if you run with the petcock at prime position?
Your VM carbs will run fine without the air filter attached.
 
Lockcuff said:
hey everyone, just got carbs rebuilt got the carbs fairly well synched at idle, bike revs fine in nuetral, but when i ride it it spits and sputters aroung 5k on the speedo, any help wouild be great, what am i missing on the carbs, i dont have the airfilter in right now either? set all screws to factory settings, got tons of fuel and new plugs
Thanks
Dan
Click to expand...
Put the air cleaner back on dang it!!!!!!!!!!!!!It will probably bog down when taking off in first without it.Mine wont hardly run without it.
 
robertbarr said:
Mine never did! Without a filter, my '79 850 ran horribly.
Click to expand...
Can't see why. CV equipped bikes, yes. VM equipped, no reason for it. Other issues in combination could cause problems.
The unfiltered VM's will simply draw more air and power will increase, even without optimum fuel/air mixture. From bike to bike, there may be a change in the powerband, but power will increase overall.
 
KEITH KRAUSE said:
Can't see why.
Click to expand...

Well, neither can I, but a stock VM-equipped bike that runs fine otherwise will run like s*(&^t without a filter.

I'm not sure why any UJM is so sensitive to upstream conditions, but that's the way it is -- and I've tried it on my own 850.
 
Definitly check to see if your jetting is right/ Also I am not familiar with your timing advance system on your bike but check to see if there are weights that fly out and advance the timing as the rpm increases, check to see that these are working properly
 
robertbarr said:
Well, neither can I, but a stock VM-equipped bike that runs fine otherwise will run like s*(&^t without a filter.

I'm not sure why any UJM is so sensitive to upstream conditions, but that's the way it is -- and I've tried it on my own 850.
Click to expand...
Then we disagree. I don't want to turn this thread into an argument over something so simple.
Only CV equipped GS's have serious (run like sh..) vacuum issues when running without the air box, with pods or velocity stacks. These bikes depend on the restrictive air box to allow the throttle plates and diapragm/spring assembly to operate as one unit. CV's are more work but they can still be tuned to run well and increase power.
VM's are simple and straight forward. Remove a restrictive air box and you increase air flow and so, power. The powerband may change, depending on how the bike is otherwise tuned, but the unfiltered bike will accelerate faster than the stock bike. It will also idle just fine. It will need to be jetted correctly, but the leaner mixture will increase power without serious vacuum issues.
If your bike ran terrible because you removed the air box, then there has to be another reason or it's just not possible.
 
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