Completed Overhaul: WONT START

[Call Me Ahab]

Okay, I've posted the same on my "home thread" I guess you could call it, but I figure I may get a more appropriate and timely response in the Maintenance section... Here goes:


All four plugs get fire. Starter works perfectly. Battery at full charge. Carbs are full of gas.

When I pull the plug after a moment of attempting to start, there is no gas on the plug, nor oil, nor any sign of gas in the chamber.

My compression reads at 60lbs the first time, 30 every time after the first.

What the HELL could I have done to this bike to ruin compression that badly?

When I installed the new rings they all fit perfectly, I gapped them myself and they were exactly to manual specs.
New valve seals, they sealed correctly as far as I could tell, butted completely up.

New gaskets across the board, o-rings too.

I redid the timing 6 times before I was satisfied with it, and I'm damn sure that it's correct.


So... in summation:

Plugs spark.
Engine turns over.
Oil level is at optimum.
No gas in the cylinders.
Low compression readings.
Battery and all electrical connections I could test are fine.

__________________

 

[Starion007]

Hello,
Have you ensured you have valve clearance?
When you said timing do you mean cam timing?
Did you make sure the rings were correct side up?
Did you make sure the rings gaps were staggered?
To determine if its rings, intake or exhaust, you can remove carbs, pipe and valve cover and set up an airline to put air in a cylinder. One at a time low pressure like 30 psi, make sure piston is on down stroke valves closed. You can then listen at the carb, exhaust port and down in the crankcase via the cam chain tunnel. this will pinpoint the leak to one of 3 locations. Sorry if this is long winded but it's a start.

 

[Call Me Ahab]

Hello,
Have you ensured you have valve clearance?
When you said timing do you mean cam timing?
Did you make sure the rings were correct side up?
Did you make sure the rings gaps were staggered?
To determine if its rings, intake or exhaust, you can remove carbs, pipe and valve cover and set up an airline to put air in a cylinder. One at a time low pressure like 30 psi, make sure piston is on down stroke valves closed. You can then listen at the carb, exhaust port and down in the crankcase via the cam chain tunnel. this will pinpoint the leak to one of 3 locations. Sorry if this is long winded but it's a start.

Valve clearance was okay before rebuild, I lapped them and reinstalled them - did not adjust valve shims.

Cam timing, yes.

Rings are installed correctly, staggered, and correct side up.

I just picked up a can of starter fluid... I'll go try to blow myeslf up - if that fails, I'll go ahead and run the air line like you suggested - thank you! Hopefully this will be an easy fix, I do NOT want to take the engine off the frame again and rip it apart >=[

 

[Call Me Ahab]

Okay... I think I flooded the damn thing.

I got it to fire, nearly started up once with the starting fluid. Going to let it sit for an hour or so and evaporate before trying again.

 

[chuck hahn]

Well one thing I keyed in on is this..the clearances were good BEFORE your rebuild and you lapped the valves..but you DID NOT redo valve clearances.

First off, if you did the valve clean up right, this would include cutting the valve seats and then lapping to see where the seats and valves are meeting up. Adjusting accordingly per each valve till centered . Cutting the seats ( if you did it ) will make the clearances up top LESS. Thus tight or partially open valves even when off the cam lobes...which means a leak and bad compression.

If you didnt cut the seats then you may have pitting and bad valve seats as well.

basically fill in these details as to what was done to the head and how you went about it. this will fill in the blanks and add more perspective the symptoms.

 

[Guest]

Just so you know, I've been putting my 80' 1000G together the same time you've been doing yours (sort of). And I had a similar problem with the initial start. Turned out that even though I 'thought' I had put my cams back together properly, I had not. Redid the cam timing and she started right up. Just a thought. And Chuck is right about the valves shims, you need to check them, so you might as well have a look at your cam timing while the tops off.

 

[chuck hahn]

I should add this..if the rebuild is fresh and the bike hasnt ran yet, the rings arent seated fully and that too may be the source of a minor bit of the low compressions. But they should be high enough to get it to at least start and get things settled in.

I would go back and recheck ALL the valves if it was me.

 

[Call Me Ahab]

I should add this..if the rebuild is fresh and the bike hasnt ran yet, the rings arent seated fully and that too may be the source of a minor bit of the low compressions. But they should be high enough to get it to at least start and get things settled in.

I would go back and recheck ALL the valves if it was me.

Check in what way? Just tolerances like the shims and whatnot?

Just so you know, I've been putting my 80' 1000G together the same time you've been doing yours (sort of). And I had a similar problem with the initial start. Turned out that even though I 'thought' I had put my cams back together properly, I had not. Redid the cam timing and she started right up. Just a thought. And Chuck is right about the valves shims, you need to check them, so you might as well have a look at your cam timing while the tops off.

Checking again can't hurt, but I redid it - SIX - times before I was satisfied with it... maybe I screwed it up after all...

Well one thing I keyed in on is this..the clearances were good BEFORE your rebuild and you lapped the valves..but you DID NOT redo valve clearances.

First off, if you did the valve clean up right, this would include cutting the valve seats and then lapping to see where the seats and valves are meeting up. Adjusting accordingly per each valve till centered . Cutting the seats ( if you did it ) will make the clearances up top LESS. Thus tight or partially open valves even when off the cam lobes...which means a leak and bad compression.

If you didnt cut the seats then you may have pitting and bad valve seats as well.

basically fill in these details as to what was done to the head and how you went about it. this will fill in the blanks and add more perspective the symptoms.

Cut the seals? I'm not sure what you mean by that - I think it's safe to say, I did not.... How would one go about doing this? I saw no mention of this on any guides D:

I'm done for tonight though, I just damn near blew myself and my bike up.
Gonna rest up, get a fire extinguisher, and hit it again tomorrow. I am less than impressed with the evening's progress.


****
What was done to the head:

I replaced the valve seals, but I did not cut them, as you said.
I lapped the valves, and they all -appeared- to seat properly and centered.

 

[chuck hahn]

TYPO...I meant valve SEATS. To do a proper valve job, you have to recut the seats and then lapping will show where the valve and the seats are meeting. You want the worn off mark in the marker you put on the valve to be about 2 MM wide and as centered between the top and bottom of the valve face as possible.

But you said new valve seats so they wouldnt usually need to be recut and refreshed. But are they fully seated and how did you insert them?

Heating the head in an oven at around 275 to 300 will allow the old seats to come out and the new ones to be inserted. Another trick is to throw the new seats in the freezer to contract them as much as possible. this aids in the insertion into the heated head AND allows you to be sure they are fully seated. Evenly heating in an oven prevents head warpage as well.

And yes we are saying to recheck the clearances at the cam and shims. seems something may be slightly holding the valves open.

 

[Guest]

OMG, you tried starting your bike for the first time after a rebuild and din NOT have a fire extinguisher handy! all kidding aside, I ALWAYS have one handy because I don't trust myself, lol. And if you haven't heard it enough....check your cam timing. You will anyways cause you've got to check your shims. Don't worry about all this, you've done the work, the bike will start it's just a matter of sorting some simple stuff out, and the more time you repeat things the simpler it gets..ask me how I know

 

[gearhead13]

Are you using stock Suzuki piston rings? I read in your other thread that you found some on ebay. Got a link to the ones you bought?
Are you sure they are the correct size for your bore and ring width etc?

 

[Call Me Ahab]

TYPO...I meant valve SEATS. To do a proper valve job, you have to recut the seats and then lapping will show where the valve and the seats are meeting. You want the worn off mark in the marker you put on the valve to be about 2 MM wide and as centered between the top and bottom of the valve face as possible.

But you said new valve seats so they wouldnt usually need to be recut and refreshed. But are they fully seated and how did you insert them?

Heating the head in an oven at around 275 to 300 will allow the old seats to come out and the new ones to be inserted. Another trick is to throw the new seats in the freezer to contract them as much as possible. this aids in the insertion into the heated head AND allows you to be sure they are fully seated. Evenly heating in an oven prevents head warpage as well.

And yes we are saying to recheck the clearances at the cam and shims. seems something may be slightly holding the valves open.

I think the miscommunication is on my end, not yours - I replaced the valve oil seals with VITON seals.( http://www.ebay.com/itm/120999388256?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 ) What are the seats? Are those the tube / channels the valve resides in? It may be that I've overlooked some critical part here =X

When I installed the new seats, I gently pushed them into place, then drove them home with a small socket. I made sure I gave each some extra encouragement to ensure proper seating. Before I replaced the valve springs I made sure that each valve sealed properly - chamber-side and within the new oil seals. None appeared to have any play, nor did the seals appear loose. They looked to be perfectly centered.

OMG, you tried starting your bike for the first time after a rebuild and din NOT have a fire extinguisher handy! all kidding aside, I ALWAYS have one handy because I don't trust myself, lol. And if you haven't heard it enough....check your cam timing. You will anyways cause you've got to check your shims. Don't worry about all this, you've done the work, the bike will start it's just a matter of sorting some simple stuff out, and the more time you repeat things the simpler it gets..ask me how I know

Indeed... I should have known better, my previous adventures with gasoline have cost me dearly...

All righty, I'm compiling a worklist for tomorrow... I'll put everything in at the bottom - thank you =]

Are you using stock Suzuki piston rings? I read in your other thread that you found some on ebay. Got a link to the ones you bought?
Are you sure they are the correct size for your bore and ring width etc?

No, they are not "Suzuki" rings, but they are made for the Suzuki bikes.

I cannot find the link to the rings..
((((GS1000 PISTON RINGS ALL MODELS 1978 TO 1981 4 SETS STANDARD 12140-49001 ( 261176208467 ) ))))

They are "HY" Brand. They do appear to be decent quality.
Yes, they are the correct rings; I triple checked - even asked the machinist who honed my cylinders. Before I installed them, I checked the gaps inside the cylinders to be sure they weren't too tight - a perfect fit according the to Suzuki manual.

Okay, so for tomorrow I need to:

Check Valve tolerances
Check Cam Timing
Evaluate Condition of Valve Seals
(Find out what my valve seats are!)

Thank you everyone! I found that I was too wound up after that fireball, I went and cleaned the GS1000 airbox I bought off ebay a while back and never cleaned up... Found a brand new K&N filter inside =D

I'll put that on in place of those cheap pods... I'm sure they're doing me no good.

Thanks again guys, I'll let you know of any further developments. Have a great night folks, sleep tight and be careful!

--- Oh lord I think I just figured out what you mean by valve seats... No, I did not replace the seats - just the seals!

 

[almarconi]

The part that the valve stem rides in is called the valve guide. The seat is in the head and is what the the valve face seals against. When you rebuild the head you should have measured everything. Sounds like you replaced the valve stem seals not the seats. The seats once installed have to be cut with special cutters at the proper angle so that they seal against the valves. It may not be necessary to replace the valve guides, valves or valve seats unless your measurements showed they were out of specification. I have overhauled several heads and only replaced valve seals since all other measurements were within the specified tolerance. As part of replacing the head you need to replace the cams and readjust the valves. I figure that I will need to do this at least 2 times. The first time to get my initial valve clearance and the second time to change any shims that are needed. If you did not do this, more than likely your valve adjustment is not correct. If you have never replaced the cams before it is possible that everything is not lined up correctly. It is very easy to be off a tooth or two, the crank will sometimes rotate a small amount and this will throw off your timing.

Compression measurements need to be taken with the engine warm so until you get the engine running I would not draw any conclusions about the compression.

 

[chuck hahn]

Ok ..so the NEW seats were actually the valve guides. I see now. And when you installed them your certain the hit fully to the bottom and are fully seated. You wiped the holes out well with some spray and Q tips or something to be sure they were perfectly spotless?

And as Almarconi said, the seats would need to be recut with the valve cutters. This removes pits, burnt spots, sets the angles perfectly to match the valves matting surface. You probably dont need new seats, but the ones in the head now should be cleaned up and reset per the factory angle specs.

New valve seats should come from the factory preground and good to go..is my impression right Almarconi?

 

[almarconi]

New valve seats should come from the factory preground and good to go..is my impression right Almarconi?

I would say no because it would depend on the type of valve job you were doing ie. 3 angle or 5 angle. Here is a picture of a uninstalled valve seat:

It looks like a metal ring. I have never cut valves seats before and more than likely would leave this to a professional since I do not have the tools or the know how. I'm sure members like rapidray would have experience doing this.

 

[chuck hahn]

I havent installed or used new ones. I have used the Neway cutters and recut the existing ones though. I was assuming the new ones would come precut. I am still learning many things as the need to fix whatever it is arises.

 

[almarconi]

Here is a link to how they are installed in a car head, the procedure should be similar to a motorcycle head:

http://www.cheprecision.com/html/install2.html

 

[chuck hahn]

The yamaha manual for the TX tells you to heat the head in an oven for even heating. This expands the aluminum faster than the seats metal and they can be removed that way.

 

[Maddevill]

Heres how to determine why your compression is low. Using the nut on the right side of crank turn until a piston is at TDC compression stroke,(valves closed). Using the adapter from a compression gauge, put air into the cylinder. Don't go too high on the psi, hold the crank from rotating with a wrench. If you hear hissing from the exhaust, your exhaust valve is not seated. If you hear hissing through the carb throat, your intake valve is not seated. If you hear air through the crankcase breather your rings are not seated or are broke.

 

[Starion007]

With the lapping of the valves even though you may not have ground them it can still tighten up the valve lash. I would go and check the valve lash clearance. I have found after a head reassembly the valve lash gets smaller after the motor is cranked over or run.
I put one back together with the lash on one valve less than the minimum and after starting it and running it the lash went to zero, and I had blow by and low compression on that cylinder.
Worth a look.