Need some engine start trouble shooting..

[thlillyr]

Ok I've read all over this forum and read lots of posts about engine not starting and how to clean them and such. But I still haven't found my answer. So I've got to be annoying and ask why my engine won't start. It is an xs400rj 1982.

Back story. Been running good for last few months but running very rich cause i hadn't had time or knowlege to tune it. Then Crashed it into a wall. Minor crash just bent the forks. Engine seemed to be running very rough after that and was difficult to start and keep running. Recently I pulled the carbs reset the idle screws to stock 1 1/2 turns and synced the carbs. Ran EXCELLENT. Beautifully clear hum. Turned it off with the kill switch put the gas tank on it now it won't start. literally 2 minutes later. WTF? Took the tank off and it still won't start. Using a makeshift bottle gas tank. Yes the kill switched still isn't flipped.

No back fire almost no popping, it's popped twice in an entire day of cranking it. nothing. Pulled the carbs again they are full of full and floats look and move good. Nice and clean. No blockages. I could do my hair in the reflection of the carbs. new battery strong crank for long periods of time.

tomorrow I will check for spark. How do you do that. Will it work like a car if you touch the spark plug to engine block to ground it?

Thats my only guess is that maybe theres no spark.

Any suggestions?

 

[JARichmond]

From my experience the spark plugs foul very easily if you can't get it to start after a few cranks. My best suggestion is to pull the plugs and have a good look at them. Also pull the gas tank back off and check the coils for anything that doesn't look the same from before you put the tank on. When you set the tank on maybe you jarred something loose? That's my best suggestion.

 

[thlillyr]

Figured it out. The spark plugs were extremely fouled. Got new ones and after some love it started and keept running. But No matter what I did I couldn't get the carbs to sync using a homemade manometer. Pulled the plugs and the right side looks new and the left side looks like the old plugs. Looks like I've lost a piston ring and compression on that side.

Anybody know where I can get a piston ring kit?

 

[xschris]

I would do a compression test first to see what you have.

 

[drewpy]

might be just rich on that side, try weakening the mix.

could also be a symptom of erratic spark preventing full ignition!

 

[thlillyr]

I rented a compression tester from auto zone but the Gage wouldn't fit the spark plug hole. Any suggestions? I've got the idle screws set to 1 1/2 turns and I visually synced the carbs. What else could i adjust to lean it out? Also when revved its slow to rev up and just as slow to drop RPMS. Could the left be rich and the right be lean?

 

[JARichmond]

Looks like you'll have to find a compression tester that fits the hole. Messing with the intake exhaust system would lean your bike out. I might get yelled at by someone for saying this, but try taking off your filters in a relatively clean area to lean out your mixture and see if that solves the problem temporarily. If it doesn't then it's probably something else.

 

[thlillyr]

Actually that's how I've been testing it. Without the air box on and with with the 2 air valves on the carb mounts are uncovered. Could my floats be totally off?

 

[HoughMade]

Well, you are running that thing so lean, you can't tell anything about how it actually runs.

 

[JARichmond]

I agree with HoughMade. You might have a super lean mixture if you're running it like that already. I had been assuming that you had been running it with the full equipment on. Try putting everything on and messing with your choke to see if any of the positions make a difference. Similarly, there are a number of manuals that you can download from the forum if you don't already have one.

 

[xschris]

Those air barbs on the intakes must be covered or you will be sucking way to much air!!

 

[thlillyr]

Actually with the barbs open and no air box is the only way I can get it to start and run sorta normal. With everything on properly it doesn't start or will barely run at all. But even running super lean like that the left side still has super black plugs after only a few minutes. I'm going to see if I can find a compression tester that fits today and let you know what I find. FYI the bike ran great before I smashed it into a wall a few months ago.

 

[drewpy]

I wonder if you have dislodged the floats so they are set rich. recheck the heights again; 26mm!

 

[thlillyr]

I FIGURED IT OUT. Fingers crossed. I pulled the carbs again and check the floats. Guess what they were set to? 18MM. Who ever had this before was an Idiot. Also it originally had 95 jets and the idle screws were closed. I am amazed it was running at all when I bought it.

Compression test was excellent. 135 both sides. But it just wouldn't run right. I pulled the Plug I had fouled earlier and cleaned it with just my finger and screwdriver. That fixed the engine knock it had developed. (I feel retarted) It still seemed way two lean I had the carb boots pluged the left with my finger and the right with the rubber plug. Just didn't seem right. So I hooked up my mano meter to check to see if my bench sync was anygood and kaboom! Bike just came alive.

Apparently I nailed the synce as the levels were perfecly still and bobbed in unison like they should. As it turns out the little rubber plug that covers the right boot air plug wasn't plugging the air. When hooked up to they mano meter it ran great.

So I think I've got it all figured out. Aside from having to fabricate a proper Idle screw bracket that was previously broken off.. This thing was really messed up from the guy before..

All I have left to do I is cram the carbs back onto the air box and test it one last time.