April 1, 201412 yr Author Right slight update. Iv found out that the bike is not actually a racing model thanks to gas gas and just a standard 250. So someone has obviously put the keihin carb on, would this make the bike pink if the reed block isnt changed as well? As i have gone two sizes up on the pilot jet which is 50 and dont seem to be having any luck with the pinking changing same with adjusting needle height. My friends going to lend me his dellorto so will see if it runs right with this on. If not anyone have any other ideas? Pottering around on the bike on first half of the throttle is fine but then when you ask for the power to do something along comes the pinking asif its getting starved.
April 2, 201412 yr Well nothing wrong changing carbs. As far as the Keihin, you need to know what model, what slide, jets. needle valve, needle jet.
April 2, 201412 yr Author Whats currently in the pwk keihin is 122 main 50 pilot as iv gone from 45 which is two sizes up. JJH needle not sure on the slide does it say on it?
April 2, 201412 yr I have seen one Keihin that got plugged up internally that had to be replaced. Need to make sure all passages blow through. I like the idea of swapping carbs to check.
April 2, 201412 yr Since the plug is black and oily it looks as if its not lean mixture that is causing pinking. It could be carbon deposits in combustion chamber, either because they are glowing causing "pre ignition" pinking or because they are raising the compression causing "detonation" pinking. PS before anyone picks me up on, pre ignition and detonation I have put them in "". Unless the squish clearance is within spec you are wasting your time messing with the carb. Also you need to know what your insert is doing to combustion chamber pressure, If it is a high pressure insert yo may need to run on Avgas or premium fuel with an octane booster.
April 3, 201412 yr Author The insert is a standard one thats all iv done put it back standard from a low s3 insert (gold) and there wasnt really enough carbon build up to say it would bother it really.
April 10, 201412 yr Author Update the bike seems to not pink as bad with a 50 pilot and needle raised to the max although it is slightly there still. But obviously running it like that it is rather rich from the amount of fuel its getting.
April 11, 201412 yr Author No my mate decided to bring the carb and not the top for it when they are different :/ His is a 300 so i presume the dellorto jets for a 300 would be different wouldnt they?
April 12, 201412 yr Jetting between the 250 and 300 is usually close to being the same. It would allow you to know if the carb is your problem.
April 15, 201412 yr Author Right thanks for that. Has anyone got a 3 slide to try out near north yorkshire??
April 15, 201412 yr Can anyone with a racing tell me if after the keihin carb do they have the rubber adapter that the airbox slots onto? If i remember rightly a while back someone made alloy adapters for the dellorto is there any for the keihin? Nope the intake from the air box fits right on the Keihin. The Delorto is the only carb that uses that. The rubber adaptor is a pain if its just not right too. Lewis Sport here in the states has them. Best investment you can make to the delorto carb. Saves you 30 minutes of swearing. --Biff
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.