Jump to content

JETTING QUESTION PLEASE HELP

Recommended Posts

I purchased a 1995 xr600r that would not run. I totally restored the bike and completely rebuilt top end. ( cylinder bored over 1mm, Weisco piston, New OEM camshaft, new OEM rocker arms, lapped valves, new valve seals, new valve springs). I also rebuilt the carb with honda jets. I went up one size on the Main which was a 155 and went up a size on slow jet which was a 65. left needle alone. also i replaced the air cut off valve with a new one. Also purchased a new honda air/fuel mixture screw. I started with mixture about 3 turns out made sure valves were adjusted properly kinda on the high side of tolerance so they are not too tight. I removed the snorkel and put a new factory honda air filter back on ,and the bike has a white brothers slip on. Now that you guys know whats in the bike im going to tell you what problems im having.    I can get the bike started and it will idle, but idles rough and the air fuel mixture screw seems to not have much affect on the condition of the idle. When i grab the bike and rock it back and fourth it kinda wants to die.( i mean grabbing the bike and holding it upright off the kickstand). But it seems like its running way rich! i can give it some throttle and black smoke comes out of exhaust and smells like gas and also i looked at plug and it was black. Now the reason i went up on the jet sizes was becasue i figured bigger  bore needs more fuel along with the added slip on pipe. im about 500 feet above sea level. Now i read that the bigger bore will actually draw more fuel and air due to is sucking on the carb harder but i read that after i had already changed the jets. Can anyone help me please?? 

Share this post


Link to post
Share on other sites

You'll have to start dropping jets one size at a time till it runs right. Should've done jetting before rebuild to get it dialed in so your not going too rich/too lean on fresh parts repeatedly. 

Share this post


Link to post
Share on other sites

My XR650L was changed from a 644 to a 675, which is a two point something bigger bore.  It didn't need bigger jets to compensate.  If anything, it would probably work better going down a size from what worked before with the stock piston, but I'm leaving it on the rich side as added protection from detonation and overheating.

  • Like 1

Share this post


Link to post
Share on other sites

My big bore 2 stroke I had needed to go from a 170 main and 48 pilot stock to a 155 main and 38 pilot just to give you an idea. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×