hard to restart when when at operating temp

jurob · Full Member Joined: May 16, 2009 Posts: 21

when cold it's a one kicker (electric start doesn't work yet). when op temp it put my right hamstring into a coma. was at a friends house and couldn't get it restarted and ended up push starting it.

as long as i don't shut it down it runs very good, but has a popping in the left exhaust off throttle coasting.

pulled plugs when hot when it won't start and they are burning very nice so i don't think its the carb.

new points and condenser by the previous owner. plugs and wires.

buddy thinks it may be the valves on the left cylinder (side that pops in the exhaust) which i will check thursday when i'm off.

i'm leaning towards a faulty coil. anybody know how to test and the specs for the coil? its a 79 special with a fresh topend.

i got the bike almost two weeks ago and didn't have any issues. starter needs the fix, but would start the bike when it is warm according to the po and verified by me. starter no longer engages at all and i'm waiting to install mike's repair gear and spring.

only thing i've done to the bike was add a left side baffle for the mac exhaust that shot out because it had the incorrect hardware to hold it in.

it also had a overflowing left side carb that i thought was a needle and seat issue, but when i took off the bowl the seat was actually a thread or two loose and leaking through the threads, which i fixed. i would leak after sitting for a few minutes.

any ideas and tips appreciated.

rob

oldskoolcool · Full Member Joined: Sep 08, 2007 Posts: 372

weak coils when they get hot maybe?

xsjohn · Last edited by xsjohn on May 25, 2009, 5:51 pm; edited 1 time in total

When hot and the bike sets a few minutes it evaporates all of the remaing charge and when you start it it is lean..........best to set the mix screws by ""cruising"" along on low throttle (on pilot jets only) and checking the plugs every few miles setting the mix screws till there is just a ""tiny"" trace of soot on the plug end ring....and the soot should be no farther than 1/3 the way up the side of the electrode........new plugs are hard to read......a few hundred miles on plugs is better.....if too much soot just wipe it off and put the plug in and go again......and setting each side individually ......

out on the mix screw for more soot and in for less.....and all this should be done at operating temperature...after at least 10 miles.....

And I make custom needles for all the XS's that provide a more balanced mixture ...........so tuning the mix screws like above then the engine is getting the right amount of fuel on the left and the right at more agressive throttle settings.....because the right runs at least 25 degrees hotter than the left at operating timperatures it requires a different mixture...................bottom line there...........

xsjohn

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Could be coils, but sounds to me that the pilots maybe a problem.

The pilot jets in these bikes are always getting gunged up.

y advice is to fit 30 Micron Briggs and Stratton Lawn Mower fuel filters. And never worry again. Clean the carbs, fit the filters and then KNOW that crap in the carbs aint the problem Smile

jurob · Full Member Joined: May 16, 2009 Posts: 21

thanks guys.
each feed has new filter. carbs are fresh.

John,
i will check the mix screws. tks!

jurob · Full Member Joined: May 16, 2009 Posts: 21

about to give up on the turd:)

doing a chop and want it running perfect before i start. hopefully that will happen in a week or two.

just tried to start it an hour or so ago. bike hasn't been run since around 10am (9 or so hours). would not start, occasional very small spurt. obviously couldn't play with the mix screws.

talked to a friend of mine; he thinks since the motor is a recent rebuild by po that the valves are too tight and not able to build suction to get fuel from the carbs. feels this is more of a problem that appears when hot, but can also happen when cold. he thinks if the carbs are clean and i get it to start on ether or carb cleaner it will be the valves.

time permitting, i will:
1. check for spark
2. adjust valves
3.adjust clutch
4. hopefully have it running to play with the mix screws.

and if i have spark, adjust valves and clutch and still have a non-start i will pull the carbs out.

xsjohn

If the timing is too advanced it is also harder to start when hot......could try retarding it an 1/8" from the F mark at 1200.........mine hasn't been on the F mark in 9 years.....and my foot don't hurt .....and it pulls better at the lower rpms.........

xsjohn

tacoswild

No compression or leak down gauge available? Would save some guessing about the valves but it never hurts to set them anyways.

Number one cause of hard starting in my time with my XS is electrical. If the battery is run down even a little it gets tough, and if the battery is old it's basically always run down a little. Or another classic is kicking for a bit, trying various amounts of choke, checking for the third time that the gas is turned on then finally noticing that when I parked last night I turned the key off with the headlight on and couldn't tell it was still on because of the sun. No way mine is going to start with any lights on. Especially on a bike that was running fine before you turned it off I'd always suspect electrical. Timing and carbs problems would have probably shown up when it was running.

pumps

Don't forget to check cam chain tensioner adjustment.

What Happened to 650rider.com?

Yamaha xs650