Topic: Can't start 750k1 after replacing head gasket

[lencomm]

Hi all, just want to say this site has been a tremendous help with problems in the past and was hoping for some insight on the latest issue. I blew one of the "puck" gaskets on the head so I tore down and installed a new gasket set. I replaced the air filter, points and spark plugs as well. My bike now will not start whereas before it started on the first kick. I did manage to start it once(barely) but it wouldn't idle, it only ran when choked and it overall ran like crap. Any attempt to unchoke it resulted in it wanting to die. I managed to get revved it up but it misfired through out the rpm range and it backfired once at about 5000 rpm. I shut it down and haven't got it started since. The plugs get wet fouled. When turning the bike over, it stumbles like it wants to start but it just won't catch. I adjusted vave clearances when the engine was out and I even pulled the engine a second time to verify that the cam and crank were in the proper position. I did notice that # 4 cyl. was at TDCC not # 1 when cam and crank were aligned. The carbs have been cleaned and floats adjusted. I have the air screw 1 turn out. There is a blue spark on all four plugs. It seems like it's not timed correctly even though I've timed it and retimed it. It also seems like it's not carbureted properly. I haven't synced the carbs but this shouldn't keep it from starting. They did work before but I could be wrong. One thing I should mention, one of the intake ports cracked so I jb welded a peice of conduit with similar dimensions although smaller in diameter by just a hair. I think that I'm getting a good seal but I can't be sure because I can't start it. I have pretty much run out of ideas and waa looking for some direction. Summer's almost over and winter lasts far too long here in the NW. Any help would be greatly appreciated. Thanks, Drew

[bowhunter]

Are you positive on the cam timing? If off a tooth or 2 woulcause lots of problems.

Bowhunter

[eldar]

With out knowing what all you removed it is hard to say. But if you had to do anything with the cam or chain, I would most certainly think it is timing. If timing is off a little, you might or might not bend valves but spark would be off and not ignite the fuel and that would cause wet plugs. Hate to say it but I would recheck to make sure the cam is aligned properly.

Maybe others have different ideas.

[jsaab2748]

 Is there much resistance from compression in the kick start lever? Take out the plugs and turn the motor over several times with the kick starter. Any binding/noises and or tight spots that might indicate valve to piston contact? Think of it this way. You need three things for the engine to run, compression, fuel and a spark at the right time. so far you've made changes that can affect all three of these requirements. Check each system separately and start with compression. If you aint got ANY compression, or have very little on ANY or ALL cylinders, suspect engine mechanicals/adjustments that would affect it. If you have 100 psi (at least) on ALL CYLINDERS, to me, this indicates that the valves are operating in time and that valve lash is reasonably close enough for the engine to run. All the rocker assys were installed back in thier original positions, right? If engine mechanics check ok, I'd look at ignition next and after that, the fuel system. JMTCW.. As a side note, Does anyone know if one of these engines will even run if the cam timing is off by just one tooth?

[lencomm]

Hi all and thanks for your replies guys. I did do a compression check and all cylinders were around 130-135 dry and about 140-150 wet. The I tore down the motor the second time just to make sure the engine was aligned correctly. I put the crank on the "T" mark for 1 and 4 and the cam marks were parallel with the cam bearing seam with the notch at twelve o'clock. The kickstarter turns the motor over and there is no binding. The motor sounds healthy kickstarting it(minus the all important running part). I timed the motor and both coils fire at their respective "F" mark. The plate is turned as far as it will go however. One thing I noticed when testing for spark. The first revolution of the engine produced nice spark but it seemed to get weaker as the starter got to speed. The spark remained fairly blue but it was somewhat diminished. On the cam towers I matched the parts with matching stamps although I can be sure that everything went back exactly where it cam out as my parts got moved around from a raccoon or some animal in the night. I did match the marks on the cam towers with the marks on the cam holders. I hope it's okay. As far as the cam chain, as long as I was able to get the chain on the sprocket with the marks lined up on the cam and crank wouldn't that be okay? The manual doesn't get more specific than that from what I recall. I also rotated the engine several times once assembled and there was no binding. Could the fact that the head and combustion chambers are now carbon-free affect the carburetion so much that it wouldn't start? Thank you very much for your time and effort. Drew

[bryanj]

You say the timing is at the "F" mark but what is the points gap? it should be 0.35mm or 14 thou I know some of the manuals quote 1/10 of that!

[lencomm]

 Thanks for the response. I used the .356mm blade on my feeler guage. Drew