Kick it over and set it on fire

Thread preview: more carb help.

I've just learned some important lessons regarding abuse and friends.

I got back from overseas a few days ago and got started on my 1980 XS650SG project. It's your now standard converted hardball bobber with sporty tank. I would include pictures but we have all seen lots of bikes EXACTLY like mine.

I got it running yesterday. Threw on a pair of VM34 carbs I got from 650 connection. My old ones were junk. Ran a new fuel line with filter, replaced fouled plugs and made a throttle cable. Pulled the chokes and it kicked first time. Ran a bit lean but I set the idle and decided it could wait another day. I wired up a headlight/taillight the went to bed. Today it was a one kick champ again and I started trying to find the right mixture. The sound of it running brought by buddy walking up the drive way. He asked to ride it and I couldn't say no. I've ridden all of his bikes and he has 10 years of experience on me. So...I thought "what could it hurt?" My drive way is 100 yards easy. I told him down to the end and back was as far as he could go. I stand proudly watching my sexy machine go to the end with a high idle all the way....then me made a turn.....then he continued down the road...then I heard 3rd and an open throttle with loud backfires.

Shit.

Ten minutes later he returned to tell me the idle was high and had trouble returning then it was low and wanted to die. He slapped me on the shoulder and said "but that bitch is fast", as he walked off. I was in shock. She wasn't ready for all of that. I looked over my battered baby to find the cover to the false oil tank was gone. My shitty wire job was all over the fucking place. I knocked on his door and made him find it. Once I had it I stuffed the wires back in and tried to kick it. Nothing. 20 kicks later I got a right carb backfire and not much else. 20 more kicks later it got a backfire that shot the carb out of the intake.

I had a bike that ran. Not well but the fucker ran. Had 150 left, 140 right, good spark and was sure that I'd be on the highway in a week. Now I have a bike that just holds up a cover in my front yard.

I know I need to start over. Recheck everything. Could be something small like one of the wires burned through or big. But I am honestly looking for a shortcut based on everyone's experience. So...help. Please tell me there is a simple step to get me back to where I was.

When you say you threw on a set of vm34's did you properly sync both of em???

XsC

My first bike was a CB550 that I coaxed a guy into selling me that was sitting in his garage covered in dust for a year. It was beautiful. Leather corbin seat, heavy custom made cafe fairing, clubman bars, electronic ignition. Gloss black front to back.

I finally got it from him by convincing his wife to convince him to let it go. He reluctantly sold it to me and I took it home. I already had my clymer's and had put together some parts and tools in preparation.

I worked on that bike for three months solid. Rain and snow, heat and cold. I had that bike in my living room on a board so I could work on it at night when I had no garage.

Finally, after months of winter work, spring came and I rolled the bike out to the driveway and fired her up and she ran and purred like a big cat.

Big black cat. I rode the living shit out of that bike night and day.

Three weeks later, my gf rode the bike to a party to show it off. While there, her coke sniffing ex-bf managed to persuade her to let him borrow the keys, and he drove it around the block high on drugs and wrecked. Slid the bike under a car, trashing it.

My now ex-gf came home at 2 am crying, talking about how upset she was that her ex had crashed my bike.

I learned an important lesson that I remember to this day. Yes I love you, no you may not have my fucking keys.

No. I had not had a chance to sync them. I hadn't had a chance to do anything.

Sounds like the symptoms your buddy was describing was that your carbs need to be properly synced! There is no bolt on and go when dealing with carbs, Especially Vm34's!!

XsC

Sgallaty, now I completely understand. It's a hard lesson to learn but it seems we all have to learn it. At least my bike isn't under a car. Thanks for helping me keep things in prospective.

I know there is no bot on and go with any carbs. I didn't go. HE went. So how do I get it running to sync the carbs?

did you do a compression test yet?

roll your crank over by hand to check the cam chain adjuster. when i ran my bike for the first time with a new cam chain, roared thru third gear, had probs running back home after short balls out run up a hill, and it wouldnt idle, then wouldnt start. adj'd the cam chain, and it cam back to life. rechecked the valves, and timing, I guesse the first run on a new cam chain needs a break in?

Headed out of town for a day or two. Tried to talk my buddy into doing the test while I was gone. He said "do you really want me touching your bike again?" Uh....no. So the test will have to wait. As soon as I get the numbers I'll post them. I want as much help as I can get.

Angus: understood. Once I check compression and spark I'll check the chain. That's honestly something I haven't done before so I'll be studying my manual.

Update: Got home this morning and started with the simple stuff. I have spark and fuel. Compression...yeah. About that. 160 right and 60 left. I am still have my fingers crossed that its a timing issue and not a problem with valves, seals or rings. Thanks for all the advice so far. I am sure I'll be back with more questions.

60 left?

60 psi. The most I could get out of it was 60 psi.

I am generally wrong about this sort of thing but it seems to me that if I have one cylinder that can hold pressure and one that is less than half of what it should be then it's not a timing issue. It seems like it would be a part from that valve/seal/ring. Wouldn't I have problems with both cylinders?

Is it possible to have one bad and one good through multiple kicks and it still be a cam issue?

do you get carb/exhaust backfiring? can you do any sort of leakdown to see if valves are even closing?

I don't think so; it'd seem that if the cam was off for one side, it'd be off for both. But, like you, I'm generally wrong, too ;-). Have you checked to make sure your carb is opening all the way for that left side?

Check and adjust the valves asap. Set your timing. Etc... Do all the simple and easy shit first, so you KNOW its good when you start digging into the tough stuff.

If they are is good nick, than try a leakdown test. Hopefully its not an internal or head issue.

Compression that low (as you know) can be a sign of some major issues, or some not so major issues.

Are you sure you did everything the same/right way when checking? Wide open throttle, etc? Im sure you did, but sometimes its the little simple shit you forget that causes issues.

Also, you said the bike backfired and blew the carb off of the bike. Did it also cause damage to anything? Is it possible that you burnt a valve, or even a piston because of the lean condition?

Def sync the carbs up as well.

After you figure it out, and get her running again you should deck your buddy in the jaw. Haha

Where are you located BTW? If Im nearby Id be glad to help ya figure it out.

backfiring that hard sounds like intake valve stuck open. what do you think vony?

132zed said:

60 psi. The most I could get out of it was 60 psi.

I am generally wrong about this sort of thing but it seems to me that if I have one cylinder that can hold pressure and one that is less than half of what it should be then it's not a timing issue. It seems like it would be a part from that valve/seal/ring. Wouldn't I have problems with both cylinders?

Is it possible to have one bad and one good through multiple kicks and it still be a cam issue?

Click to expand...

each cylinder operates independently of one another with its own set of valves.

i bet it will fire over with new plugs in them, but not long since you got a 60 on one side, i just hade to do a valve job on one of my motors was getting about 60 on both sides

sgallaty said:

backfiring that hard sounds like intake valve stuck open. what do you think vony?

Click to expand...

Very well could be. If it was running REALLY lean, you could have a shit valve seat as well, or even a bad valve now.

Massive backfires are bad news.

You really need to do a TOTAL inspection and make sure nothing is broken. Chances are you're ok, but better safe than sorry.