Why Won't You Start!!!

[Guest]

Ya know this valve adjustment thing really has me baffled. My 850 valves were wayyyy tight and not only did it start really easy but it also ran very good. As a matter of fact all of em were too tight for the feelers. Granted they were loose enough to rotate the bucket but every single one of em were out of spec.
Not to argue, the valves need adjusted but how dang tight do they need to be for the bike not to start?

The 850 is now within spec and other than a little more noise I cant tell a dang difference.

Seems as long as you can rotate the bucket then the valve arent stuck open, the bike should run.

 

[tom203]

I'm arriving late to this , but I need an Adler summary.
1/ first carb cleaning- no good but bike still ran?
2/second carb cleaning- not better but bike still ran?
3/ bought carb cleaner, soak carbs, changed o-rings, but now it won't start?
I'm sure it needs a valve adjustment, but why doesn't it start? Are your plug wires on correctly? doublecheck,cuz this is easy to do in haste.

 

[Adler]

I'm arriving late to this , but I need an Adler summary.
1/ first carb cleaning- no good but bike still ran?
2/second carb cleaning- not better but bike still ran?
3/ bought carb cleaner, soak carbs, changed o-rings, but now it won't start?
I'm sure it needs a valve adjustment, but why doesn't it start? Are your plug wires on correctly? doublecheck,cuz this is easy to do in haste.

almost... after the first carb cleaning it didnt run... after the second it did run but not too well. I had carb cleaner the whole time but I bought a jug big enough to dip things in for the third cleaning

I thought about the plug wires being wrong but then it wouldnt run on starter fluid would it?

 

[Guest]

No tank... everything exposed... pull all the plug wires, pull the plugs and make sure they are damp. Now put fresh plugs, recheck the plug wires carefully. Choke the snot out of it and don't touch that throttle... After that doesn't work, check the dang valves. When you are done with the valves, let us know how it runs... We are rooting for you...
Curt

 

[tom203]

I thought about the plug wires being wrong but then it wouldnt run on starter fluid would it?

That's a point to ponder- since the plugs fire twice in the four stroke cycle, I wonder whether the ether could still go bang with miswired plugs.I guess I'll have some more coffee now.

 

[Adler]

Alrighty guys,
I finally checked my valves and here is what I found;

Cylinder     Shim In     Shim Ex     Clearance In     Clearance Ex
    1          2.70        2.67          <0.0015         0.0025
    2          2.70        2.70           0.0025         0.0025
    3          2.70        2.75          <0.0015        <0.0015
    4          2.65        2.70          <0.0015         0.0015

I realize that I mixed metric and imperial measurements here.
The point is ALL the buckets turned freely so I would think that these measurements are not far enough off of spec to cause my no-start condition (I'd be delighted to be wrong). Of course, I'll still change the shims to make them all perfect but in the meantime I'd like to figure out why its not starting!

 

[BassCliff]

Hi,

The spec in inches is .001-.003. It seems half of your valves are too tight and one more is at minimum. (I find it easier to measure in millimeters, .03-.08).

Do you have the airbox installed?

Since it catches with starter fluid but then dies, it seems like a fuel issue. If the airbox is not installed then you could be running too lean.


Thank you for your indulgence,

BassCliff

 

[Adler]

Hi,

The spec in inches is .001-.003. It seems half of your valves are too tight and one more is at minimum. (I find it easier to measure in millimeters, .03-.08).

Do you have the airbox installed?

Since it catches with starter fluid but then die, it seems like a fuel issue. If the airbox is not installed then you could be running too lean.


Thank you for your indulgence,

BassCliff

The airbox is indeed installed. I agree that it sounds like a fuel issue but wouldnt it have to be VERY lean for it to not even sputter? And if the carbs are at fault, can't it run on 2 or even 1 cylinder? meaning ALL the carbs would have to magically have stopped working after i put in fresh o-rings!

Puzzling indeed... When I have more time later this week I may switch the carbs for a spare set I have to see if that will do it.

 

[Steve]

It still amazes me how many times advise will be ignored/rejected because "it can't possibly be that because ..."

Tight valves are notorious for causing hard starting on cold engines. Part of the reason is that the valve will be held open later due to the tight clearance. This allows some of the mixture that is in the cylinder to be pushed out the intake valve, back through the carb. The carb does not care which way air is moving, it sees moving air, more fuel is added. Moments later, the piston is going back down, the valve is open, air goes back through the carb AGAIN, picking up even more fuel. To add insult to injury, the "choke" is probably set, making the mixture far to rich to even think of burning.

This only happens when the engine is cold because of metal expansion. The head expands as it warms up and clearance from the cams to the valves will increase a bit. Hard to say just how much, but it must be enough to help the valve timing and starting problems.

How tight do they have to be to cause this hard starting? I have not been able to measure that point, as it is smaller than the thinnest feeler in any set I have ever owned. The last time I had a bike with those hard-starting symptoms, I don't remember if the buckets could be rotated or not.

Bottom line: adjust the valves. Keep them well-adjusted. Record your results (see the bottom of my sig).
In the first four hours after you asked the first question, valve adjustment was discussed more than any other topic.
In fact, it was mentioned just four minutes after the question.

However, nobody mentioned one other tip: THROW THE STARTING FLUID AWAY.

If the bike won't start, fix the problem, don't thow "band-aids" at it.

.

 

[Adler]

Thanks Steve, I hope you're right and its just the valves, I just assumed that if the valves werent too far off I would at least be getting SOME action out of the engine. I knew from the start the valves were a suspect but I also knew they would take me the longest to fix and I definitely didnt want to find it wasn't the valves causing the issues (though I'd do them anyways, I know how these bikes are finicky like that).

As to the starting fluid, I would never use it to start the bike! It is just a diagnostic tool, if it burns with the starter fluid then I doubt the problem is electrical in nature.

 

[resjudicata]

Sounds to me that you reassembled the carbs wrong in some way. The tiniest mistake could prevent the carbs from operating correctly.

How many times have you rebuilt these type carbs? Anybody local that could go over them with you to make sure you get them assembled right?

Oh, BTW, adjust the valves.

Chris

 

[Guest]

won't start

won't start

Did you take the carbs,compleatly apart and follow the instructions for carb cleaning from this web site? I didn't hear you complain about getting the Air screws out most people do. You said the time it did start idle was high that's a sign of a air leak. I think you have some combination of problems. Recheck what you know is right, it might be wrong. Happened to me. When you do the valves, on the GSTWIN site there is a video of a Guy adjusting valves on a GS 500. Basically the same operation it was good help to me on my first time. I built a 1980 GS1000 from scratch my very first try at it. With a lot of help from this site. Now the bike screams down the road trying to get me a speeding ticket. It's not magic stay with it brother, it wants to run. Once it doe's, don't even sit on it without all you gear. Good helmet ect..

 

[Adler]

Did you take the carbs,compleatly apart and follow the instructions for carb cleaning from this web site? I didn't hear you complain about getting the Air screws out most people do. You said the time it did start idle was high that's a sign of a air leak. I think you have some combination of problems. Recheck what you know is right, it might be wrong. Happened to me. When you do the valves, on the GSTWIN site there is a video of a Guy adjusting valves on a GS 500. Basically the same operation it was good help to me on my first time. I built a 1980 GS1000 from scratch my very first try at it. With a lot of help from this site. Now the bike screams down the road trying to get me a speeding ticket. It's not magic stay with it brother, it wants to run. Once it doe's, don't even sit on it without all you gear. Good helmet ect..

Yup, followed the VM carb rebuild guide on BassCliff's site and redid all the o-rings courtesy of Robert Barr. Im not sure what air screw troubles you're talking about though, maybe the broken bits of airscrew some people have stuck in the hole? Thank goodness, these carbs didn't have those troubles.

I'm almost done with the valves, switched around some shims and now I'm up to ordering some shims to fix the few trouble valves. Here is where the clearances are as of now;

Cylinder     Shim In     Shim Ex     Clearance In     Clearance Ex
    1          2.70        2.67          <0.0015         0.0025
    2          2.70        2.70           0.0025         0.0025
    3          2.70        2.70          <0.0015         0.0030
    4          2.75        2.65          <0.0015         0.0020

On Sunday I plan on going over everything, and maybe even switch the carbs for a spare set.

 

[Adler]

Alright! Update!!
Took me a long time but my valve clearances are DONE!!!

Here is where they are now;

Cylinder     Shim In     Shim Ex     Clearance In     Clearance Ex
    1          2.62        2.67           0.0025         0.0025
    2          2.70        2.70           0.0025         0.0025
    3          2.65        2.70           0.0030         0.0025
    4          2.60        2.65           0.0025         0.0025

This is how they started;

Cylinder     Shim In     Shim Ex     Clearance In     Clearance Ex
    1          2.70        2.67          <0.0015         0.0025
    2          2.70        2.70           0.0025         0.0025
    3          2.70        2.75          <0.0015        <0.0015
    4          2.65        2.70          <0.0015         0.0015

Thanks to Ghostgs1 and the valve shim club for making it easy.

Anyhow, I will shortly try to run this thing again and see if my issue was just the clearance, though somehow I dont think so....

 

[Adler]

Update again... I tried to run it again... no dice... VERY frustrating. I think my next step is to pull the carbs (AGAIN!!! ) and investigate... If that still doesnt work, its on to points and condenser.


EDIT: Anyone know how to test the points and condenser? That would be helpful...

 

[tom203]

Update again... I tried to run it again... no dice... VERY frustrating. I think my next step is to pull the carbs (AGAIN!!! ) and investigate... If that still doesnt work, its on to points and condenser.


EDIT: Anyone know how to test the points and condenser? That would be helpful...

You have double checked coil wiring to make sure that spark plug leads didn't get switched? Valves ok, fuel to carbs- all it needs is spark at RIGHT time .

 

[Adler]

You have double checked coil wiring to make sure that spark plug leads didn't get switched? Valves ok, fuel to carbs- all it needs is spark at RIGHT time .

Yup pretty sure about the plug leads, I even tried with them switched just in case...

It WILL run on quick start (I know, I know, bad idea) which indicates to me that either the spark is too weak to ignite the fuel or its not getting fuel from the carbs.

 

[spyug]

I share your pain....been there and now....back again....sort of. Back last fall and winter I rebuilt my 82 Katana project. The engine had been seized but I got that sorted and the carbs were completely redone as per the standing rules and regs of the GSR. The bike would not run. There is a huge long thread on this topic buried somewhere in the archives. The bike did eventually run and i had it tuned like a Swiss watch.

After languishing 5 months this summer I'm back on the project now and I can't get her to run on cylinders 3 and 4 ( there's a help me thread on here now too). now it will run on choke only. If I blow into the overflow hose , 3 and 4 will kick in but then die so gas is getting to the carbs. There is lots of engine vacuum and spark. Gas is not flowing through the carbs however. I pulled, recleaned and rebuilt the carbs yesterday but saddly no change.

Originally back in the winter I tried everything to get it to fire and nothing until someone suggested a novel approach. Disconnect or remove the airbox or pods and cover the mouths with "clingfilm" ( i.e. Saran Wrap etc). Poke a tiny hole in the center and with choke on crank her over. Once warmed close choke. I did this and it ran perfectly. Once running and warmed I removed the film and it continued to run fine and start and run there after. I don't know the whys and hows but it did work.

It did take a bit of cranking so I added a deep cycle auto battery in parallel for some extra cranking amps.

I just remembered this overnight so haven't got to try it again on the Kat but I will later.

You might try this too.

Good luck,
Spyug.

 

[resjudicata]

Yup pretty sure about the plug leads, I even tried with them switched just in case...

It WILL run on quick start (I know, I know, bad idea) which indicates to me that either the spark is too weak to ignite the fuel or its not getting fuel from the carbs.

If it will run on starting fluid then most likely you are not getting gas for some reason. You need to pull the carbs and check them over carefully to see what is preventing the carbs from delivering fuel. You may not be filling the float bowls for some reason. Or, if the float bowls are full them your jets aren't transferring fuel from the float bowls to the throat of the carb at the proper ratio.

BTW, if you question whether you are getting spark you should use a timing light to check. Simply connect the light and turn the motor over while watching the bulb of the timing light. A regular pulse to the light shows spark. Do this for each cylinder. Also, pull the timing cover and use the light for the timing marks to make sure you have the right leads on the right cylinders.

My bet here is the petcock not delivering fuel to the carbs, or the float valves not allowing fuel into the float bowls, or pilot jets that are dirty again and/or not fully cleaned.

Chris

 

[Adler]

Today I had a burst of motivation so I pulled the carbs and cleaned out the tiny holes in the bottom of the float bowl (that lead to the enrichment circuit) then I transferred all the things missing from my spare rack over to the spare rack and I reinstalled the spare rack.

Filled it with gas, flicked the switch and tried kickstarting it (the battery is weak, didn't want to stress it too much with starting) nothing happened... (besides the engine turning over... obviously...). So I did what noone on here likes, I sprayed one or two seconds of quickstart in the airbox, it fired up and much to my amazement it stayed ON!!! I adjusted the idle and it hums pleasantly around 1500, I could maybe turn it a little lower and Ill try that later.
Now I just wonder if my other rack of carbs is the problem or if the float bowls was the problem. A question for another day!