Hi all

Im a proud owner of a Montesa Cota 315R and Have just got hold of a Gas Gas JTR 250 1996

So here is my dilemma

I have trouble with the bike running at low revs

I started by cleaning the carb , took all jets out blasted them with cleaner and can see daylight through all holes .

New spark plug and air filter

Bike just wont idle properly , so could the pilot jet be too small ( although it did run fine about six years ago)

I wondered if its got corrosion and isnt letting enough fuel through .

It will only idle with the idle revs screw in quite a bit and wont settle down to a nice pop pop pop , just revs a bit higher and them drops right down and dies.

It wont then start without the choke , although once the choke is turned off it still runs , so hopefully that means it is getting idle fuel etc.

the Plug gap seems small its 0.25 and on my Montesa its .080 so a big difference .

Any help would be very much appreciated

Marcus.

Carb cleaner is not enough, you need compressed air.

Thanks , I will try and get a new Pilot jet and save any second guessing .

hi Sherlock,

sounds to me like you got an air leak, most obvious would be a split in the inlet rubber between carb and reeds you might have to take it off to have a good look at it, they get very hard and brittle with age so it might not be sealing properly.

Other thing to look at would be the stator side crank seal these can fail as they are dry on one side, if the bike has been standing for a long time it would be worth giving the fly wheeland stator a clean.

You will need a puller for the flywheel,you would be welcome to borrow mine. I live in Folkestone too.

check the rubber first, these bikes are no where near as finicky as modern bikes, if the carb looks clean I think it would run.

I assume you have a good plug in the bike.

TLTEL

Hi , I also thought it might be an air leak , but I have taken off the connection between the carb and reeds .

It looks ok no cracks .

Its actually my friends bike who is just starting out with trials, not saying im an expert!

He has taken the carb off again this evening to blast the hell out of it with a compressor .

I was hoping it would not be an air leak on the crank seal , I have never had to delve that deep yet !

I have been spoilt with my Montesa as it seems to never play up , with just oil changes , carb cleaning and new plugs every now and then .

Thanks for your advice I will keep you posted .

P.s It is a new spark plug , but the plug gap is 0.25 which I was unsure of , I found it on line but not 100% sure of its credibility.