surging

[jefft]

I am trying to get bike to run right after rebuild. Its a 77D with Boyer ignition, Shell cam, stock carbs. Starts up but at idle it seems to be speeding up and slowing down. Has the good carb holders from JBM (I think thats the name of the company). Timing seems to be on and I checked it with timing light. Momentarily speeds up a little then back down to idle then back up a little. I have a color tune and the mix seems pretty close. By the way I think turning the screw out richens it but how far out can I go?
Jefft

 

[nightowl49]

make sure you have no air leaks in your intake side that will make it wander around also check cam chain adj

 

[xjwmx]

I have a color tune and the mix seems pretty close. By the way I think turning the screw out richens it but how far out can I go?
Jefft

I think with the Colortune you richen it until flickers of yellow begin to appear. I'd love to have one of those but I'm not going to pay what they're asking.

 

[jefft]

Right after I asked the questions I checked the cam chain and had to adjust it a lot. I turned the nut in quite a ways until the plunger was even with the end of the housing with engine running. Its still surging and I'm thinking I might need to get larger pilots. This is the first time I used the colortune so I may not know exactly what color I should be looking for. The first time I used it I had the air filters off as well if that makes much difference I'm not sure. I am going to let it set overnight and adjust the valves and see what happens now that I have moved the cam chain adjustment so much. I think they should be at .006 intake and .012 for the exhaust with a Shell cam but correct me if I'm wrong. I had a place called oldskookcarbs rebuild the carbs with new throttle valves seals to. The carbs came back looking great but I'm not sure how he jetted them. I will check the timing again now too. Done some looking for a 77D I believe its 1 1/4 turns out on carbs.
jefft

 

[5twins]

Let me get this straight - you bought a Boyer, a Shell cam, and paid someone several hundred dollars to rebuild your carbs ..... and you don't know what jets are in them ???!!!!

I've run '76-'77 carbs on my mildly modded '78 (pods, pipes, minor porting). This carb set came with the smallest main ever put in a 650, a 122.5. It was done because the midrange was the richest ever used (Z-8 needle jet). Still, this carb set can use some help on top. Bump your pilot up one from the #25 stock to a 27.5. Increase your mains to 130 or 132.5 and lean the needle one step. That'll be $175.00 please, lol.

 

[jefft]

Ok, so I should have had a look before I put them on the bike. I had told him what modifications I had made and he jetted with what he thought it would need but who would know for sure until you start it and see how it runs. Its been over a year ago and I just don't remember exactly.
jefft

 

[jefft]

Interesting find after removing carbs today to look at jetting. The pilot is a 127.5 but the main which look new is clearly marked 44. Needle jets Z-8's. I have never heard of a 44 main jet. There is an up and down mark before the 44. I guess its a 144. The progression should be 142.0 to 145.0. Whats up with that. Clip was in the lowest position making needle at its highest setting.
jefft

 

[grizld1]

There's no such animal as a 127.5 PJ. I suspect you have your MJ and PJ sizes interpolated. If the Boyer ignition isn't getting sufficient power it will advance, and if power to it is erratic it will advance erratically. When it advances, idle speed will climb.

 

[jefft]

There's no such animal as a 127.5 PJ. I suspect you have your MJ and PJ sizes interpolated. If the Boyer ignition isn't getting sufficient power it will advance, and if power to it is erratic it will advance erratically. When it advances, idle speed will climb.

Sorry about that I mean to say pilot 27.5. I have used a magnifying glass and looked at that main every which way and it is stamped 44 or 144.
Jefft