Won’t Run

[Shipper]

So rode for a few days and couldn’t get over how well my 75xs 650 was running. That was then. A few days ago it started to break down on start off accelleration but would still run well at higher rev. Now, won’t run longer then a couple of strokes before quitting. Pulled bowls off carbs - everything appears normal. Checked spark at plugs - again normal. Need your suggestions/recommendations guys.

Frustrated - it was running soooo good.

 

[yamageddon]

Are you running points? Check/change the condenser (or condensator). Or the points self of course...

 

[azman857]

How's the battery? It she charging?

 

[Shipper]

How's the battery? It she charging?

Battery charges no problem. Thanks

 

[Shipper]

Are you running points? Check/change the condenser (or condensator). Or the points self of course...

Are you running points? Check/change the condenser (or condensator). Or the points self of course...

I am and I will. Thanks.

 

[grizld1]

As the old saw goes, the combustion tripod stands on three legs: ignition, compression, and fuel. Get a manual--links to free downloads of the factory service manual for '78-'79 are in the Tech section, and ignition service specs given there will be exactly the same for your XS650B. Now--instead of playing whack-a-mole, procede systematically. First: set cam chain tension and valve lash and make sure fuel is fresh. Next: clean ignition connectors. Then with the tank off, headlight bulb removed, headlight shell open, and main switch on, check voltage at the battery and compare it to voltage at the coils. If there's more than 1/2V drop in voltage at the coils, look for the cause; check voltage on the brown wire into the kill switch and the red/white wire out of the kill switch. Then inspect the points, gap, set static timing, and finish timing with a strobe. If no joy, check compression, drain tank and install fresh fuel. If still no joy, come on back.

 

[funky]

check air holes on fuel filler cap, or air leaks intake manifold ATU my be not working right ....just a few ideas

 

[Brassneck]

I'd check/clean the carb--specifically the jets. A small blockage is all it takes.

 

[Shipper]

As the old saw goes, the combustion tripod stands on three legs: ignition, compression, and fuel. Get a manual--links to free downloads of the factory service manual for '78-'79 are in the Tech section, and ignition service specs given there will be exactly the same for your XS650B. Now--instead of playing whack-a-mole, procede systematically. First: set cam chain tension and valve lash and make sure fuel is fresh. Next: clean ignition connectors. Then with the tank off, headlight bulb removed, headlight shell open, and main switch on, check voltage at the battery and compare it to voltage at the coils. If there's more than 1/2V drop in voltage at the coils, look for the cause; check voltage on the brown wire into the kill switch and the red/white wire out of the kill switch. Then inspect the points, gap, set static timing, and finish timing with a strobe. If no joy, check compression, drain tank and install fresh fuel. If still no joy, come on back.

Brilliant Grumpy. Feed loose in headlight cluster and two coils loose on the base (how the Fr%^$K did that happen). Running like its right out of the box.

Thanks again.

 

[grizld1]

Well done, Shipper. (To answer your question: age, vibration, and gremlins are usually responsible, alone or in collusion).