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| 250cc and Above Engine Tech Technical Discussion Forum for 250cc and up Engines |
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#1
01-15-2012, 04:07 PM
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250cc Cornering issue..
Hi all, we picked up a coolster 150 last year and after a bit of fun we picked up a 250cc and with some modification/welding/shoehorning and kicking, managed to get it in...
Everything went well and after a bit of playing with roller weights and the like it behaves the way we want, really torquey down low with little high speed, cause we only run it in mud or in fields.. The problem comes with hard cornering, turning/drifting/donutting, going left is fine but try to do it the other way and the buggy splutters badly as if she's not getting fuel.. We modified the inlet manifold to level the carb out as when we fitted the new engine it meant the carb was off level a bit, but this did'nt help.. Anyone have any ideas?? One other thing, when we fitted the petrol tank we did'nt use the original and the one we are using does'nt use the vacuum fuel pump, it's just gravity fed, do you think modifying it to run the vacuum pump would help? Thanks... 
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#2
01-15-2012, 10:26 PM
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I'm a firm believer in gravity feed!!! Does the sputtering occur when your cornering on the far end of the tank outlet?or- is the fuel moving away from the outlet? I've had to elevate my tanks some to help eliminate this issue when doing donuts and cornering hard, that fixed this problem.
How about some pic's of the shoehorning of the 250cc in the coolster.
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#3
01-16-2012, 04:33 PM
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Will get some pics up soon, should really have taken more when the work was being done...
I don't think that the tank orientation would affect it but I will definitely look more into the position and height a bit better... I just could'nt understand how it would have a lack of fuel just from cornering hard, surely the petrol in the bowl should be sufficient to keep the carb fed...
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#4
01-16-2012, 07:09 PM
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Simple explaination- if the fuel in the bowl get's pinned to one side for any length of time and the fuel in the tank leaves the pick-up dry momentarily it sucks air that runs over the top of the fuel causing it to sputter, if the carb is already at it's low limit on the float level due to engine orientation then this occurs very easily- through a few engine transplants I've found that just a 1/2" change in the angle of the engine/carb makes a huge difference as I keep managing to mount all of them WRONG!!! and have to find the right angle for the carb before it runs right. Having a 1/4" fuel line also helps. I moved the tank on my "different type of buggy" up 2" and solved this issue- I kept thinking it was some other issue all along.
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#6
01-22-2012, 03:22 PM
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I owe you some thanks Metal, I took your advice and made a new tank in work the other day and fitted it this morning...
All cornering issues are now gone it seems...  I have a couple of pics here of the buggy in it's current state, don't be too critical as it's a work in progress, the idea being to get it in a good mechanical state and then do a neaten up on it...     This one above shows where we took the shaft from the 250 eng and the one from the 150 eng, and spliced them together so that we could use the reverse sprocket setup that we already had in place... lots more to be done but it goes well enough for now... The one below is a video, klik it... 
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