Gas Gas GP250 setup

[Rich19]

Hi,

In need of some help/advice recently got back into trials bought a second hand Gas Gas 250GP 2019.

I can’t get it to run right kicks first time from cold, warms up but constantly racing like the choke is on and smoking a lot can’t get the mixture and tick over scew right it then will stall and won’t kick over again. Plugs not oiled up and running 75 ml to 5 litres 

Any help would be greatly appreciated.

[jonnyc21]

Dose it have an aftermarket adjuster screw for the idle or mixture?  They can often cause issues.  

[Rich19]

Yes it does for both I will try swapping them 

Thanks 

[jonnyc21]

Once you are done doing that let us all know how things are going and I am sure someone here can provide some good feedback on next steps if needed. 

Edited June 25, 2023 by jonnyc21

[collyolly]

I have the same bike, not used for a couple of years now but at the time I could not get it to start easily, in the end I changed the head and insert for the low compression version and the engine was transformed.

I think the standard GP is probably set up for ‘modern’ expectations when in reality you just want an easy bike to ride, just my thoughts.

 

[sherpa325]

On 6/25/2023 at 2:26 AM, jonnyc21 said:

Dose it have an aftermarket adjuster screw for the idle or mixture?  They can often cause issues.  

Why would they cause issues, I have them on my bikes with no dramas

[jonnyc21]

13 hours ago, sherpa325 said:

Why would they cause issues, I have them on my bikes with no dramas

I have had both a number of friends as well as seen several others online have issues with them.  It seems to be inconsistencies in the tip shape and/or thread cut that can cause it.  Most of the ones I have seen issues with have loose threads and air can get by them, but the tip shape can make it hard to get the adjustment spot on as well. 

Not all of them have issues but its been often enough for my buddies and I that a quick trouble shooting check is to go back to stock and see if it sorts out the issues.  If it doesn't fix the issue I usually work on jetting first then go back to the aftermarket adjusters after I get the bike running well and make sure the bike still runs good. 

In the end it isn't to hard to swap them in and out so its one of the easier checks and has had a high enough positive result set when I have done it that I find it worth the suggestion. 

 

PS. come to think of it a touch of some thread tape might work to seal up threads... not sure on that but maybe worth consideration at any rate. 

Edited June 28, 2023 by jonnyc21

[sherpa325]

I always use the S3 ones on all my bikes including twinshocks and using genuine Keihin carburetors and have had zero problems on any bikes and I am very fussy.