New Build Idle issue

Howdy All!

After a Lengthy rebuild (mostly because I was riding my other bikes ) I tried starting my bike and I can get it to fire but not idle.

so what I have done to the bike is:
- Complete engine over haul new everything.
- VM34s jetted for XS650
- PAMCO ignition with coils and wires
- PMA alternator
- Capacitor, no longer running a battery
- New throttle cables
- I set the tensioner/Valve clearances

When I do get it to fire, if I keep the idle above 3000RPM it will run but soon as I let off it sputters and dies out. could it be something to do with the idle screw being set too low ? or is my timing too far out of whack ?
I did set my throttle cables so they lift the slides up at the exact same time and all that good stuff and there is no hang ups.

any advice would be greatly appreciated!

Thanks

You need to make sure your slides are set to a base opening, not just synched to open at the same time.
You can set them with a 5/32" drill bit to start off with. Then go from there. It should at least idle.

Read this one:
http://www.amckayltd.com/vm34-36.pdf

I will check that thanks

It's possible that your PMA does not produce enough power to run the ignition at lower RPM's or the capacitor is too small, so try connecting a battery in place of the capacitor and the PMA for test purposes.

Good Point! Ill try that tomorrow. What I did tonight was, check the gap on the slides and they were all good. while doing so tho I noticed one of the air mixture screws on the one cylinder(left) was turned almost all the way in and the other one was out a fair bit so I turned it out to match the other one and adjusted the idle screws a bit and i can get it to idle for 15- 20 seconds then it starts backfiring and I get backfiring and exhaust blowing out of my left carb. One thing i forgot to mention earlier is that I put a brand spanking new timing chain on the bike and it was extremely tight. I had read on here that they will loosen up after being run a bit... now that should change the tension and what not as it breaks in correct? so should i keep going back and adjusting it and doing the valves every time ? Im also thinking that it is running very rich on the pilot as i have turned the air screws out a fair bit and it seems to be helping.

The cam chain will loosen as it gets used. All chains stretch a bit. Make sure the cam chain adjustment is correct and check it periodically, as it will change. And this needs to be done, obviously, before you adjust the valves. It will change them too.
Each bike is different, so you need to adjust the air screw per your bike and your mods; like exhaust, pods, ect. Do you know what size jets you have?
I would really try Pete's recommendation first, but remember that the air screw turned in (clockwise) reduces air, thus richening the mix (opposite of the BS series carbs) which you are doing correctly. I think the recommendation is 3/4 of a turn out to start with. But, as with my bike and mods, I had to go up a size. Anything more than 1-3/4 turns out and they need to be changed.
The backfiring is usually caused by too lean a mix or timing.

He doesn't have bs carbs, lilbill. Vm's

angus67 said:

He doesn't have bs carbs, lilbill. Vm's

Click to expand...

Yep, I know. That's why I said the air screw is opposite to the BS. Turning it clockwise richens on VM, leans a BS. And to set the slides at 5/32" to start with.