Rotating engine with valve shims removed - big problem?

[c.smith]

Hi all. New member, new motorcycle owner, and new DIY-er here, so please bear with me.

I recently checked the valve clearances and changed the shims on my 1997 Suzuki GS500. One reference I used was this video, which states at 9:45, "Note: Do NOT rotate engine with shims removed." Well, I did this, and what's more, I left the bike in this state for 3 months (dealer ineptitude + my own laziness = took forever to acquire replacement shims).

I was unable to ascertain why this is so bad as to warrant an all caps and underlined "not," or what the effects would be. As such, I hoped I could just finish the job and everything would be fine. Now, I've finally put new shims in and attempted to start the engine, and it won't start.

The battery has been safely stored inside and charged regularly, and the lights all work, so I don't think that's the issue. Fuel drains out of the carb float bowl when I loosen the appropriate screw, which, according to my maintenance book, indicates that access to fuel is not the issue.

I replaced the spark plugs before doing the valve clearance check and went on a single test drive afterward, so I doubt they are the problem. One caveat: I neglected to turn off the choke when I rode with them, which I heard can foul the plugs. They also did appear to have some black gunk on them, which I tried wiping off with a paper towel, to no avail. Still, a 30 minute ride wouldn't be enough to foul brand new spark plugs, would it?

This leads me to think that the problem is compression, and might(?) have been caused by messing up the valves when I rotated the engine without valve shims. I don't yet have a compression gauge (will probably order a ~$20 one soon), so I can't check if compression is indeed the culprit. Am I right to be worried about this, or is rotating the engine without shims probably not a huge deal and my startup troubles likely stem from something else?

I'd greatly appreciate any clarification or advice that anyone more knowledgeable in the ways of engines could provide.

TL;DR: Would rotating the engine without valve shims significantly damage the engine, and/or cause compression problems which prevent the engine from starting? Or should I look elsewhere to get my engine started?

[uberkron]

Are your shims on top of buckets? I wouldnt have thought that not having full valve lift could cause piston to valve situation.
____________________
i ride a zip 50 2smoke. It overtakes a hundred times a day.

[jjdugen]

The worst you could have done would be to score the bucket face, this is much softer than the shim metal. You would have had to be pretty aggressive to do even that though.
Far more likely that you have an induction air leak if it ran for half an hour with choke on. And yes, that's more than enough to foul your plugs. Check that they are still sparking as a first step.

You say it ran for half an hour, did it run well or were there any issues? Bit more info needed.

Cheers.
____________________
The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
Try Soi 23 on Amazon for a good read.... Self promotion? Moi?

[Pete.]

Forget the shims and cams, you went for a half-hour test-ride so they aren't a problem. Besides, if you didn't touch the chain tensioner it'll still be timed correctly.

Remove the carbs and service them. Leave the tops on, but pay close attention to the choke plungers and their circuits and also the one/two tiny pinholes that are next to the bottom of the throttle butterfly when it's closed plus all the gubbins in the float bowl. I use carb cleaner, compressed air and an acupuncture needle to clear them out.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stinkwheel]

I presume it ran ok on your test run?

I would imagine they tell you not to rotate the engine because when you have the shims out, you also have at least one cam off and the camchain loose. If you turn the engine like this, it makes it marginally fiddlier to set the timing again when you reassemble.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Aff]

I don't think he has got the bike started after the valve job.

I read it as he changed the plugs before the valve job and took it for a test ride to see if the plugs worked, then he changed the shims and it hasn't run since.
____________________
Current Bikes:Honda 929RR Fireblade, Honda CD200 Benly (Project), Stomp Z2 140
Electric Bike Project

[Fizzer Thou]

For future referance Wemoto sell replacement shims

https://www.wemoto.com/bikes/suzuki/gs_500_k3/03/picture/valve_shim_2.25_mm/

From what I remember the last time that I worked on a GS500 Twin it is shim-on-bucket and a special tool is used to depress the bucket that the shim sits in.The shim can then be accessed without having to remove the cams.
The only reason that I can think of as to not rotate the engine without the shims in place,is because the lip that holds the shim in place can snag the edge of the cam and possibly damage both.When I sorted the shims on this particular GS500 that I was working on,I measured the clearance,removed that shim to check the size and then put it back into place while checking the others.A list was then made of the replacement shims that were needed.Some dealers do an exchange system where there is a small charge,which keeps costs down.

As to the reason as to why the engine will not start,I would suspect the battery.If not used they can sulphate a cell or two.If you try jumping from a car battery see how that goes.
A compression check will point you in the right direction,as this may well point to gummed up piston rings or valve seats which are corroded.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[Fizzer Thou]

This is the shim tool required to perform the job easily

https://i27.photobucket.com/albums/c187/kap0429/DSC08710.jpg

https://i156.photobucket.com/albums/t40/basscliff/maintenance/valve_adjust/depressor.jpg

https://www.ebay.com/itm/Motion-Pro-Valve-Shim-Tool-Suzuki-Yamaha-08-0017-GS550-GS750-GS850-GS1100-/171114169086
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[stinkwheel]

In that case, the most obvious cause for a) Poor compression and b) Not running following a re-shim is that the timing is not set correctly.

I'd suggest re-checking the valve timing.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[J.M.]

The usage of the proper bucket compression tool should not upset the timing in any shape or form on the GS500. Rotating whilst they are removed would also not upset the timing, but others have noted that it could cause little damage to other components such as the bucket surface/cam lobes.

The timing on the GS500 is measured between Arrow #2 on the exhaust camshaft and Arrow #3 on the intake camshaft. The arrows should point directly at a pin in the cam chain. There should be 18 pins (including the 2 that the arrows point at) between the two arrows.

This website shows how to do/check the timing: https://beergarage.com/GSTiming.aspx
____________________
2004 R1 & 2018 XSR900

[Pete.]

[prawny1]

turning a Valve above bucket set up would risk scoring the cam lobes,

turning a valve under bucket could damage the bucket itself or cause a collet to pop off as it is the shim that stops the bucket touching the spring collar, if the bucket is off you could score the lobe and risk popping a collet off.
____________________
hellkat wrote:

Some people are only alive cos its against the law to kill them.

[Pete.]

[prawny1]

Agreed cam timing would only be disturbed on a shim under bucket engine since the cam needs to come out to get the bucket out,

judging by the video op posted this is a shim over bucket engine so no such risk or reason to remove the cams.

Have you double checked that the new shims give you the correct clearance and that you checked the clearances with the engine in the correct part of it's stroke to begin with. compression check would show if the valves are being held open.

Next would be to check that the leads are on the right cylinders. and that no clips or wire have been left undone.
____________________
hellkat wrote:

Some people are only alive cos its against the law to kill them.

[J.M.]

The GS500 is really simple.

Shims sit on top of the buckets. Buckets are compressed and the shims can be removed/replaced. Even if the wrong sized shims are inserted, it should still start or gurgle in to life so long as one of the cylinders is working. Mine ran on 1 cylinder whilst warming up due to an issue. Said issue caused my RHS exhaust clearance to range between 0.4 to 1.5mm whilst cold. The position of the pistons shouldn't matter whilst checking the clearance, so long as the lobes of the camshafts aren't pressing down on the shims.

The HT leads can only connect to the correct cylinder. There is a coil for each cylinder. The left cylinder's coil is on the left side of the bike. The HT lead from the left coil will not reach to the right cylinder.

My first check would be to see whether or not there is a spark.

Additionally I'm presuming that the spark plugs were removed to make turning the engine by hand easier. If you try and turn it with the spark plugs in, can you feel a strong compression stroke? I wonder if the new spark plugs have been reinserted too loosely and have not crushed the washer to create a seal. I made that mistake putting fresh plugs on my XJ, it wouldn't start. I torqued them up to the specification in the book and it ran (albeit badly because I messed the jets in the carbs up).
____________________
2004 R1 & 2018 XSR900

[andym]

Sorry I haven't read all the replies word for word.... but I have run a bike (OK test rode) a bike with shims that were way out both ways and the only problem I found was anything over .2mm either way and the bike ran like shit.... the most I was ever out was about .6mm under and .4 over.... neither of which caused any engine piston or bore damage (that wasn't already there).

Basically the closer you get the shims to manual spec. the better the engine will run... allegedly, I always settled for 'good enough' though

On a little side note I found the shims on 2 zxr 750 engines weren't exactly spot on, and rather than paying £4 per shim I decided to get a micrometer (about £7 from lidl) and used varying grades of sandpaper and got them to within .02 of manual spec (micrometer got a bit hazy with anything more precise).... OK so it took about 2-3 weeks to do the 8 that were out after mixing and matching to find the better sizes (I found I had a shit load of .6 when I needed a lot of .35's

[c.smith]

Thanks so much to everyone who's chimed in so far, it's been enlightening and helpful.

To clarify a few questions people had:

1) I have not gotten the bike running after changing the valve shims. The test run was after changing the spark plugs, but before messing with the valves at all.

2) The bike didn't run well when I left the choke on during the test. It kept wanting to stall and die when I stopped at lights, which confused me until I turned the choke off at the end of the ride and the engine picked up.

3) I did use the specified bucket compression tool. I was pretty thorough in checking the new clearances, but I haven't taken a look at the engine and double checked anything after putting the tank back on and failing to start the engine. That'll be my next step if a compression test turns up positive.

To update:

I bought new spark plugs and they didn't fix the problem. I haven't checked for a spark yet because I was too afraid to start a fire in the parking garage. Maybe there's very little risk of that, I don't know, but I'm being cautious (I also had recently spilled gasoline in the area, and didn't have a fire extinguisher on hand...)

I've ordered a cheap spark tester and compression gauge, which should arrive tomorrow, so my plan is to do those tests and go from there.

I also might try jump starting from a car, as suggested by Fizzer Thou, to eliminate the possibility of the battery being the problem. This still seems very unlikely to me because my multimeter indicates it's fully charged and it seems to be doing fine powering the lights etc. Is it still possible that the battery is the culprit despite these indications? I'm not really sure what it would mean to sulfate a cell. Also, it's an AGM battery, if that makes any difference.

Thanks again for everyone's input so far, I'll continue to update and ask questions as the situation progresses.

[Pete.]

If the battery was cranking it well before, it should still be doing it now. Won't harm to check but beware because if you are cranking from jump leads it'll turn faster and might start because it's pulling fuel through the carbs better, making you think the problem is the battery when in fact it's the extra revolutions pulling in fuel that you wasn't getting before.

Take out the plugs, put them in the caps resting on the engine and crank it over to check for spark. You won't start a fire that way - I have tried to and failed. Don't crank the engine with a plug out of the cap though, it's bad for the coils.

If you have a spark, service the carbs.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[J.M.]

Servicing the carbs is a good call.

I have no idea why, but whenever my GS was sat for ~1 month unused, the floats would start sticking. It would either refuse to start or start leaking fuel through the airbox.

Haven't a clue why, as the carbs were absolutely spotless inside.
____________________
2004 R1 & 2018 XSR900