Difficult to Start, and refuses to idle

[7mJoe]

My bike is very difficult to start. I've replaced the petcock and had the carbs rebuilt, and everything associated with a rebuild. I know the carbs get fuel in the prime position, but the bike takes forever to fire up when I try to start it.

I'm not sure if I have a spark issue or not, but I've replaced the plugs after the last set were black and worn, probably haven't been replaced since I bought it.

I'm pretty sure I have the airbox and everything sealed well, and I'm getting vacuum from the port on the carbs; however, I am worried about a fuel delivery issue.

See, once I get the bike running, it sounds like a champ and all the cylinders fire but then it dies after about 30 seconds, I noticed some slight bogging at around 3-5k rpms but I'm more concerned about why it stalls every time I get it running. Then after it stalls, It refuses to start back up.

I'm running out of ideas and any help would be awesome! I've done some searching but can't quite find the answers I'm looking for. If you need more information let me know, I can tell you whatever you want. Also, can anyone direct me to a diagram of vacuum lines and what goes where!

Thanks!

[BassCliff]

Hee Haw Howdy!

If you need more information let me know, I can tell you whatever you want.

Forgive my silly question. What kind of bike do you have? Year? Model?

Also, can anyone direct me to a diagram of vacuum lines and what goes where!

Here's one for most GS bikes:

http://members.dslextreme.com/users/storagecliff/images/hose_locations.html

You're welcome to stop by my website and see if there is anything that might help you.

You say you "had the carbs rebuilt". Unless it was a forum member who did it for you, there's no telling what really got cleaned and rebuilt. To my inexperienced little bike mechanic brain, what you describe sounds like it could be a combination of a fuel delivery issue and valve adjustment.

Are you sure the carbs have been cleaned and rebuilt properly? Many members have gone through their carbs three times or more before they were really clean. Have you checked the float levels? Have you checked the valve clearances? Are you using a stock airbox or pods? There must be no air leaks in the intake system. Your bike will not run without some kind of air filter.

There's a good checklist here: http://members.dslextreme.com/users/..._Greeting.html

Keep us informed.

Thank you for your indulgence,

BassCliff

[7mJoe]

I have an 82 550L, completely stock. I had my carbs done by a motorcycle tech, however, I'm not exactly sure on the extent of the job he did. I have not checked the float levels, or the valve clearances, not sure how.

I have the stock airfilter. I can't say that I'm 100% sure there are no leaks in the intake system, but I'm pretty sure it's sealed well, I did my best to make sure of that.

[zach_denver]

I know you said you replaced the petcock, but I have a simple (<2min) test you can try...

Kink and clamp the vacuum-line coming from the tank (or disconnect it from the tank and obstruct the opening with something.) Put the tank on "prime" and start it up. Make sure there are no kinks or obstructions in the gravity-fed fuel-line (e.g. a blocked fuel filter).

Why do this? I had a 550 with a leak in the petcock. Evidently, gas would leak into the vac line, flood the engine and cause the engine to stall.

You can try clear fuel-line to help diagnose delivery problems:

http://www.motionpro.com/motorcycle/tools/view/clear_pvc_fuel_line/

Best-of-luck,

Zach

[psyguy]

since you are resonably confident about the petcock and the carbs and the intake...
i would check the valve clerances and the engine compression first

[7mJoe]

Ok, checking compression sounds like a plan. Can you explain why the valve clearance would be off? How does that happen? Now, if my airbox isn't properlly sealed, how can I check for this? Is there a way to check the coil packs are creating spark? With a miltimeter or something? Thanks for the help, I'll give it all a try!

[psyguy]

valve clearances get tighter as the valves set into the valve seats
minor air leaks at the airbox wouldnt explain your symptoms so you can exclude that
carb-to-engine boots should have no leaks however (check/replace the orings on those boots and check the boots for cracks)
since the bike "runs like a champ" when it does start you need not worry about the sparks
however, you can take the plugs out, plug them back into the caps, let them rest on the engine, crank and watch for sparks
also, put the bike on the centrestand, remove the carb bowl drain screws and with the fuel tap on "prime" see if the fuel flows freely from the bowls

[7mJoe]

So I've begun to check the valve clearance on my bike and if I'm doing this correctly I've come to find that cylinders #1, and # 2 (exhaust side) are beyond spec. I couldn't even fit a .0015" gauge in! I believe at this point I have to change some shims! So, my question at this point is what do I need to change my shims?

Now that I've checked, and found that the valve clearances(of at least 2 cylinders) are off, is it safe to say that this is my problem?

edit: 0.015" is the same as 0.038mm, now... am I reading my feeler gauge wrong? Would that still be in spec. or no? Because I've read spec. is anywhere from 0.03mm to 0.08mm. I'm getting confused here. Someone please explain this to me... educate me.

[almarconi]

Did you check the voltage going to your coils? If you have less than 12v you may want to consider the coil mod. Mine started much easier after I rewired.

I had my carbs done by a motorcycle tech, however, I'm not exactly sure on the extent of the job he did.

This could be part of the problem..you could have dirty carbs, wrong jets or fuel valves installed. Unless I really knew and trusted the mechanic, I would not assume that they were rebuilt/cleaned correctly.

I will probably get yelled out for this but I would hold off on the valve adjustment until you can get it to start and at least idle. Do the basic items first like check compression,clean the carbs, make sure you have a clean airfilter, plugs, check plug wires and measure coil voltage..etc.

[Suzuki mad]

Valve clearance......

So I've begun to check the valve clearance on my bike and if I'm doing this correctly I've come to find that cylinders #1, and # 2 (exhaust side) are beyond spec. I couldn't even fit a .0015" gauge in! I believe at this point I have to change some shims! So, my question at this point is what do I need to change my shims?

Now that I've checked, and found that the valve clearances(of at least 2 cylinders) are off, is it safe to say that this is my problem?

edit: 0.015" is the same as 0.038mm, now... am I reading my feeler gauge wrong? Would that still be in spec. or no? Because I've read spec. is anywhere from 0.03mm to 0.08mm. I'm getting confused here. Someone please explain this to me... educate me.

You can buy feeler guages that are in imperial (inches) or metric hence the sizes you are asking. Standard valve clearance is between 0.03 and 0.08mm or 0.001 to 0.003" [inch.]

The shims are made in 0.05mm (0.002" [ inch]) gaps so in theory you take the shim out and flip it over, look at the size on the shim and then replace with a shim that is 0.05mm smaller to fall within the 0.03/0.08mm (0.001/0.003") range.
Factors to effect that are that the shims wear down where the cam lobe runs on the so the shim could be worn. You need to use some micrometers to check the shim size.

If your exhaust or inlet valve has so little clearance it means that the valve is close not to close so on compression the whole cylinder is not working to correct method. Its compression may be down slightly. With the gap set at it largest (0.08mm[0.003"]) the valve is open for the shortest setting. Compression show be at its best.

An open valve aloows more fuel in but does not allow fuel compression hence the lack of power as the spark plug will not burn all the fuel due to low compression. Performance will drop.

Hope that helps. Other will probably chip in and add to what I have said and if I have it wrong, correct me.

To change the chim you need a pair of tweezer (like ladies use to pluck there eye brows) or long nosed pliers and a 'bucket depressing tool.' [Suzuki sell these but at £70 in the UK dam expensive.] You fit the special curved tool under the cam shaft and onto the edge of the 'bucket' that retains the shim. As you press the tool onto the but and under the shim the 'bucket' depresses the valve and the gap between the shim and the lobe becomes greater and you can use the tweasers or long nosed pliers to remove the shim.
You can use and edge of a flat blade screwdriver but that is not recommended. If you have a local Suzuki dealer you can ask politely the workshop to see if they will lend you the tool to do the job or soruce one from e**y. Some of the guy's on here may know where you can get one from.

Suzuki mad

[rudy]

Not to say that you shouldn't do everything else mentioned here, but sounds to me like a fuel delivery problem. 30 seconds is enough to empty the float bowls. After they're empty, it won't run again until they trickle full again. Could be float valves, petcock, filter, junk in your tank. You have fuel in your tank, right? I know it's a stupid question, but it's easily overlooked.

I would find out exactly what this motorcycle tech did to your carbs. Did he dip & blow out, replace jets and gaskets?

[robertbarr]

Petcock:

http://www.cycleorings.com/petcock.html

For carb cleanup, see The Garage section. There's a thorough pictorial.

For the valve clearance adjustments (shimming), see BassCliff's step-by-step procedure. You can't go wrong.

[don_gibb6512]

Don't forget to test the resistance of your coils. Bad coils can cause this problem. 3-5 ohm primary, around 30K ohm secondary.

[psyguy]

a 'bucket depressing tool.' [Suzuki sell these but at £70 in the UK dam expensive.]

wtf

hey, suzuki mad, you know these are available from z1 for like us$15, right?

[7mJoe]

I think what I'll do is send the carbs in to get professionally rebuilt. I honestly have no idea on the extent of the rebuild job the guy did, and I'd rather someone who knows what they are doing rebuild them for me. After that hopefully it'll run, and if not then I'll know for sure it isn't the carbs.

If it does run after I get them done, then I'll look into replacing the shims. Been working on this bike now for a year, why not make it two! I'll let you guys know what happens.