No start, help

[gabordi]

Hi, I just finished to assemble the 555 kit and I am now trying to start the motor but it doesn't start anymore.

I checked it there is fire to the spark plug that works. I checked the valve timing about 15 times ( both notch on the cams facing each other, arrow 1 facing head deck, arrow 2 up with 1st pin and arrow 3 of the intake cam up facing the 18th pin) and all this while the rt mark is facing the left pick-up coil. There is some gas that goes in the cylinder (it smells).

I tried all day long to figure the problem but found nothing. Maybe someone more experienced could help me to find a way to start the motor.

The engine is rotating freely. I am thinkin to take a compression test to see if there is no big leak.

Thanks a lot, gab

[fred]

Hi there. If the engine ran before you modified it, I'd start with the things you changed as most likely candidates...

What exactly happens when you go to start it? Does it crank forever and not do anything? Does it blow the carbs off the bike? Does it catch every once and a while, but never long enough to actually start running on its own? Does it backfire a bunch? Does it catch fire? Are all of your interlocks doing what they're supposed to (side stand interlock, neutral switch, clutch switch, kill switch, ignition)?

You checked to make sure you had spark, that's good. Are you sure it is enough? Bright blue versus yellowish? Is the spark gap set correctly? Do your coils meet spec when you test their resistance? Did you accidentally swap wiring somewhere and connect the wrong coil to the wrong side of the signal generator?

You checked your timing and are confident it is correct, also good.

You said there was some gas getting to the cylinder, is it enough? If you made your cylinder bigger it will need more fuel, how did you set up your carbs? Did you leave them the same as they were? Did you guess based on someone else's report of what worked? Did you just straight up guess?

If you changed your carb setup, did you cause some problem when you put them back together? Are your float heights good? Are there giant vacuum leaks somewhere that are throwing everything off?

Are your valve clearances good?

Do you have compression? Is it what you think it should be? Is there something obvious going on like a massive difference between cylinders? You said the engine is rotating freely. What do you mean? Do you mean it isn't hard to turn the engine at the signal generator or back tire or just that it can turn through a whole revolution without making terrible noises or doing bad things like running pistons into valves?

Is your battery fully charged? If it sat for a long time while you worked on the engine, it is possible it doesn't have quite the amount of power required to turn the engine over and provide good spark, especially since the larger pistons are probably harder to compress. If the compression ratio stayed the same and you made the cylinder bigger, doesn't that mean it takes more effort to do a compression stroke? This is further complicated by the fact that taking the spark plugs out to test spark will decrease the amount of work the starter has to do and could deceive you into thinking you have enough power to turn over the engine and generate spark at the same time.

I'm no great expert, but those are the things I'd go after first... Go for the low hanging fruit and do the easy stuff first... If I were you, I'd post a big list of all the things you've tried and what the results of your tests were. The more specific you can be, the better. There is a pretty good chance you've missed something that another forum member will be able to point out right away.

[gabordi]

Thanks for the long reply!

First I just want to say that the engine is turning without any noise or weird thing and it needs a little effort to turn it (on the signal generator)

I tried to inverse the coil pack wires from the same coil and from one coil to a nother... no difference.

My spark is not a big fat blue one but it is a nice blue spark.

I already cheked if all the  interlocks were all set good.

I changed the carb settings but nothing huge, I'm now running 155 main jets (instead of 150 from last summer) and the clip from the needle one notch lower and 3 and half mixture screw. The carbs are well assembled for sure.

When the engine is cranking, I ain't got any kind of poffing or nothing, I only hear the starter cranking. I got maybe 2 exhaust back fire but those were the only 2 combustion I had from today! lol. For the battery, it is ok because I am boosting it up with a running car.

The cranking speed is not as strong as the original piston but fairly strong enough to start the engine.

I listed a couple of things that you suggested to me and will test them tommorow.

If anyone has other things to check and we did not think of, post it and I will try it, I wanna hear this born again monster!!!!

Thanks gab

[The Buddha]

The head if its shaved you're gonna have to time it right. May not be possible without degreed cam sprokets.
Cool.
Buddha.

[the mole]

If it has compression, fuel and spark at the right time it has to go. Without being able to see it, my money is on the timing being 180 out. Am I right in thinking that models with two ignition pickups time on a different one to the ones with only one? Have you got the right manual for the year model?

[bill14224]

If the heads aren't shaved I think Fred's suggestion is good to check that the coil connections aren't reversed.  If the left plug is sparking when the right plug should be it'll never run!  He described the timing process correctly so I doubt there's a problem there, and his carbs are staying on the bike! 

The bike ran before he started this project, so it's doubtful he has any bad components.  After that, I say gather a few guys, or find a nearby hill, and push start the bike in second gear.  My bike almost always fires right up, but once in a while when it's cold and very humid I have to crank it for 20 seconds or so on full choke before she'll fire, then it's buh-bump.... buh-bump... buh-bump... buh-bump, buh-bump, buh-bump, bump, bump, bump, bump, bump, bump, bump, bump, bump, bump, vroom! 

[gabordi]

I got the head shaved but not that much (0.5 mm). I would say that the timing is 180 degrees out too but all the indicators are ok (talking about the arrow on the sprockets). I did not touched the pick-up coils so I don't figure how it could be inversed. I will check later in the day the compression of the motor. And I already tried to crank the engine more than 20 seconds with choke And without choke.

Will give some info later about the comp

[ATLRIDER]

"When the engine is cranking, I ain't got any kind of poffing or nothing, I only hear the starter cranking"

Doesn't sound like you have much compression.  That's were I'd start.  All valve clearances in spec?

[gabordi]

I don<t have acces to a compressor gauge today, I'll have it tommorow but I think it could be possible that I have a loss of compression because there is almost no air that is blowing out of the pipe.

Are you talking about the valve to piston clearance? If yes, I don't know whats the matter with that clearance if the motor is cranking while no weird noise is comming out???

thaks gab

[ATLRIDER]

Gab,

I was referring to the clearance btwn the base of the cam and valve shim.  Let us know how the compression test goes.

[fred]

I don<t have acces to a compressor gauge today, I'll have it tommorow but I think it could be possible that I have a loss of compression because there is almost no air that is blowing out of the pipe.

Are you talking about the valve to piston clearance? If yes, I don't know whats the matter with that clearance if the motor is cranking while no weird noise is comming out???

thaks gab

If you have no compression gauge, you can always use your thumb. Cover the spark plug hole with your thumb, if you cannot keep your thumb over the hole while the bike is cranking no matter how hard you try, you probably have enough compression. If it isn't enough to push your thumb out of the way, you've got compression problems. It isn't as accurate as having a gauge, but it might be enough to indicate a problem...

[gabordi]

Ok, here is a little update.

The compression gauge is locked in a locker at the job and nobody have the key before monday so I tried fred's method just to see, like he said, if I have any big problems of compression and YES, I have some because I can let my thumb over the plug hole easely! Nice, I'm happy to found that there is no compression beacause it is a god strat to begin tests so i'll check the valve adjustment, maybe I inversed the shims like altrider said.

I am now in a job brake so I will do tests when I'll be back home at 5.

thanks gab

[gabordi]

Finally... we found the problem.

Problem is that all 4 shims are too big. Why?... because I did not mentionned it earlier because I tought that it was impossible to be the cause of the problem. I did asked to the machine shop to shave the head but I asked to do a valve job too (cutting the valve edge and the valve seat) so there is now some materiel missing between the vavle and the seat. all this put the valve stem higher than it was before and the cam always push it down.

I will buy new thinner shims and try them... maybe 0.6mm thinner.

thanks gab

[ATLRIDER]

Hi Gab,

So what are the actual valve clearances.  In spec clearance should be btwn .03-.08 mm

This link may help you decipher the right sizes.
http://www.bbburma.net/Documents/ValveAdjustmentVideo/GS500_Valve_Shim_Selection_Chart.pdf

Good luck.

[gabordi]

Thanks for the link! I go to the dealer today and bought a 2.15 shim to see what clearance I have after that becasue the shims are now too tight... all of them.

I'll get the shim by this week.

[~*STEPH*~]

I've been reading this thread because it's really similar to my situation.  I'm doing a compression test this weekend, but how do I check to see if my timing is out?  And if it is, how do I adjust it?