Suzuki GS400 valves clearances

[Andy24]

Hi,im changing the shims on my Suzuki GS400 '79 4v,the clearences now is:
1cil...I: 0.25 E: 0.25
2cil...I: 0.35 E: 0.25
The manual says that the clearences must be between 0.03 and 0.08 but i think that its too little clearance between the shim and cam,i dont want to damage anything.
I will prefer to take the clearances to 0.10 or 0.15...what you guys think?

measures are in mm...thanks for the help

 

[Nessism]

You can realistically extend the range from .03 - .11 or so, but I wouldn't run the bike with any valves at .25+mm. Something wrong. Hopefully you don't have a bunch of bent valves.

 

[Andy24]

the bike have 35000km and i dont think the valves was ever checked..

 

[Nessism]

the bike have 35000km and i dont think the valves was ever checked..

The valves tighten with mileage, the clearance goes to zero, it doesn't increase (typically). This is why failing to check the valves can destroy the engine; after a while the clearance goes away and then the valves never close, and they burn up shortly after (if you can get the bike started that is).

Good on you for checking the valves. It's amazing how many people don't.

 

[Andy24]

So i can take all the clearences to 0.10 (the exhaust valves dont need more clearance?) and than check the clearance every 6000km? (maybe 5000km for my peace of mind) like the manual says...

 

[Guest]

The valves tighten with mileage, the clearance goes to zero, it doesn't increase (typically). This is why failing to check the valves can destroy the engine; after a while the clearance goes away and then the valves never close, and they burn up shortly after (if you can get the bike started that is).

Good on you for checking the valves. It's amazing how many people don't.

Given that the clearance is with the heel of the cam which theoretically never wears, the only way the clearances could grow is if the cam bearing caps are seriously worn. It might be worth pulling at least one off and having a look. But maybe somebody back when just set them up loose or used a .011 instead of .11mm. There are some bucket and shim motors that run a stock clearance of about .012 as I recall, such as Fiat twin cams, so I don't think that much damage would occur; however, some cams have quietening ramps on them which take up the slack more gently at the start.

 

[tkent02]

I'm thinking the OP is measuring wrong. Or the guy before him did.

 

[Andy24]

im 99% sure my measurements are right, i measured all the valves 2 or 3 times with 2 different feeler gauges, im not sure if someone before me checked the valves or changed the shims,after all this years all is possible,maybe someone had wrong infos about clearances,all the valves have the same clearance except the intake of the 2nd cilinder,i can check that cam bearing cap if its worn...
at the end maybe someone replaced the shims wrong because alot of things on the bike was wrong mounted,to tighten,loose,,when i changed the clutch plates someone before me mounted after the pressure plate the steel plate and not clutch plate,fortunately after i changed the plates with new and in the right order everything worked fine...
ill check the cam bearing and if its alright can i take the clearances to 0.10mm?

 

[tkent02]

The Suzuki spec is the spec is .03mm - .08mm, since they do get tighter with wear a lot of us prefer about .06mm to about .10mm, I have gone a little bigger like .12mm temporarily when I didn't have the right shim. Never heard of one as big as .25mm, would have thought it would spit the shim out or crack it or something. Certainly check the cam bearing surface, can't imagine that much wear without making a bunch of noise but who knows?

Let us know what you find out.

 

[Gorminrider]

Hi,im changing the shims on my Suzuki GS400 '79 4v,the clearences now is:
1cil...I: 0.25 E: 0.25
2cil...I: 0.35 E: 0.25
The manual says that the clearences must be between 0.03 and 0.08 but i think that its too little clearance between the shim and cam,i dont want to damage anything.
I will prefer to take the clearances to 0.10 or 0.15...what you guys think?

measures are in mm...thanks for the help

Why would you think the manual is wrong?...if only because Your valves are not going to open quite as wide and be later too if you use larger clearances...and I would guess they are going to hammer and tapppppp quite a lot.

 

[Andy24]

i dont think the manual is wrong,i ride my bike alot on the open road in summer is fine but in the city the temp rises high and i dont wont the exhaust valves to extend too much and damage the engine if it runs now with 0.25 and 0.35 clearance,can run well with 0.10 too i think...

 

[Nessism]

You risk spitting out a shim with the clearances at .25+

 

[Steve]

You risk spitting out a shim with the clearances at .25+

You still have to over-rev the engine to do that, as the lip on the bucket is over 1.5 mm.

.

 

[Guest]

Hi Andy, Have you checked your shims sizes? If they have never been changed previously, I think they would be between 2.70 - 2.95. If you have very, very thin shims you could have that much clearance on a low mileage engine. What are the miles or kilometers on the bike? Any chance the valve seats are new?

 

[8ball]

Hi,im changing the shims on my Suzuki GS400 '79 4v,the clearences now is:
1cil...I: 0.25 E: 0.25
2cil...I: 0.35 E: 0.25
The manual says that the clearences must be between 0.03 and 0.08 but i think that its too little clearance between the shim and cam,i dont want to damage anything.
I will prefer to take the clearances to 0.10 or 0.15...what you guys think?

measures are in mm...thanks for the help

.25 is HUGE! You are absolutely sure it is .25mm, and not .025mm? There should be no reason they should get that much clearance. These motors do run a tighter tappet clearance than I am used to, my R6 upper limits are in that range (.2 and .3mm), but not these motors

The Suzuki spec is the spec is .03mm - .08mm, since they do get looser with wear a lot of us prefer about .06mm to about .10mm, .....

Valve clearances do not get looser, they get tighter. The mechanism of wear is not the friction of the cam lobe against the shim, but the valve base repeatedly trying to beat itself into the valve seat. As it does, the valve sits higher in the seat and the stem gets closer to the cam lobe. Valve clearance growth is an indication of an abnormal wear condition.

 

[Andy24]

Hi Andy, Have you checked your shims sizes? If they have never been changed previously, I think they would be between 2.70 - 2.95. If you have very, very thin shims you could have that much clearance on a low mileage engine. What are the miles or kilometers on the bike? Any chance the valve seats are new?

the bike have 35000km the shims sizes are 3x 2.60 and 2.65

 

[Guest]

Andy, I think 8ball must be right. I've never heard of those kind of clearances before. Double check your clearance readings, with the mileage on your bike these sizes would be likely. Surely you are only just slightly low in the clearance range? Ray

 

[Andy24]

now that you mentioned about your r6 i remembered that the bike was at a yamaha service before i got it,the previous owner said that this service was terrible they returned the bike running on 1cil(fortunately just a bad contact from the coil),they destroyed the gear of the start motor and carbs out of sync...maybe they changed the shims for bigger clearances(i would not be surprised).
when i removed the shims only 2 shims had numbers on it the others didnt.
if it matters the bike is for german market (20 kW) the modification to restrict the bike is in the head, camshaft profile i think...
today i remeasured the clearances and i have the same results...
at the end of the next week i should have the new shims i ordered,i will put them in,recheck the clearance and if its all good i will start the bike and see if sounds better...

 

[Guest]

Thanks for the update, looking forward to hear what your results are like. I'll bet it is much quieter! Ray

 

[Andy24]

hey guys,i finally got the parts i needed,after i changed the shims when installing the cam caps i needed to do some other work to the head cause all the exhaust threads of the cam caps were damaged,i put some helicoils in it and changed all the bolts,hell of a work cause i broke one of the bolt in the head(at low torque),all the old bolts was stretching,the cam caps looks a bit scratched but i can feel only a few scratches,after that i wanted to change the gaskets on the engine when its already open,the valve seats are good,the top of the valves looked a bit demaged but in specs(not less than 4mm) im guessing that maybe because of that the valve clearance was loose (http://postimg.org/image/mieaaiwhp/), the engine started after maybe 10-13 good kicks (before i changed the clutch plates i didnt start the engine for 6-7 days and then i needed to kick a lot more,im pretty sure because of the loose valves),the engine sounded really good with a perfect idle,ill take it today for a ride.
ill maybe try to find another head from some different market so i will have 26kW and not 20kW,and in better shape