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compression diminishes to nothing from 1 to 4

  • Thread starter Thread starter Paul's Zuki
  • Start date Start date
The rings are supposed to have some outward spring to them. There's what's called the "free end gap", which measures the gap in the uncompressed spring. That's a measure of how "springy" they are. Yes the rings need to be compressed to get into the cylinder.

Please don't tell me that we're 100 posts into this and you have not been consulting the manual? Should be some pics in there of cylinder installation. Suzuki has an official ring compression tool; most of the ones you'll find at an auto parts store are for pistons that drop in but for the RBC motors we need something we can un-wrap entirely. Quite doable with large enough hose clamps or just finger pinching.

Did you buy oversized rings? I cannot imagine that new stock rings would have too small a gap when placed in a used cylinder bore. If you filed the ends of the rings you may have lost your stamped reference for which side is up.
 
I have been consulting the manual. But I guess some things are just beyond me due to my lack of know how and this being my first time. I will add however that over the last 3-4 weeks, I have learned more about 4 stroke motors then I ever have. They do have some outward spring to them actually, but i guess after I filed them of course that "free end gap" was wider and sat really loose on the ring grove. I'm just curious if I took away some of the springiness, if you will, by doing that. Yeah, they were oversized rings, by 1.00mm.
 
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I don't think I'd pull the head again at this point, just the head cover. Please post pics of your timing mark on TDC and the side shot of your cam gears.
 
Paul's Zuki said:
I have been consulting the manual. But I guess some things are just beyond me due to my lack of know how and this being my first time. I will add however that over the last 3-4 weeks, I have learned more about 4 stroke motors then I ever have. They do have some outward spring to them actually, but i guess after I filed them of course that "free end gap" was wider and sat really loose on the ring grove. I'm just curious if I took away some of the springiness, if you will, by doing that. Yeah, they were oversized rings, by 1.00mm.
Click to expand...
So, do you have oversized pistons and bored out cylinders too? I hope so.
 
Like some others believe, it seems more and more likely that something is askew with the valve timing. Don't know what it is, but the symptoms are pointing in that direction.

Happens more often than you think, even to experienced engine builders. I had been building engines for years and I once somehow managed to misaligned the cam timing marks on a big-block 440 mopar. The cam timing was so retarded that it wouldn't rpm past 4,000 rpm's on a motor that had previously been red-lining at 6,500 rpm! It was a lot harder to correct that problem in a auto engine than it is to fix a like problem on a bike engine. Live and learn.

Before you take anything apart, carefully analyze what you currently have. Me, I would take the cam cover off and carefully observe the action of the #1 cylinder valves as I rotate the engine 720 degrees (two complete revolutions for a four stroke) from #1 firing TDC mark back thru to #1 firing TDC mark. At firing TDC both your valve buckets should be loose. As you rotate the engine thru about 180 degrees the exhaust valve should start to open. As you approach 360 degrees the exhaust valve should close and the intake open. As you approach 540 degrees (1 1/2 revolutions) the intake should close. As you get to 720 degrees both the valve buckets should be loose again.

If you have access to a Leak Down Tester and a source of compressed air I would do a Leak Down Check before I took the engine apart again. It will show you exactly where you are losing your compression.

Most good machine or engine building shops should have a Leak Down Tester. Or, if you know anybody in General Aviation (GA), a pilot or a mechanic with a light airplane, they will have a Leak Down Tester as it is the ONLY way that you test compression in a piston engine airplane.
 
yeah, every set of piston rings I have ever seen for my bike either specify 1.00 mm or .50 mm oversize. am I getting something I'm not supposed to?
 
Yes, you need standard rings. Not oversizes.

Paul,

I'd like to see you succeed. Feel free to call me if you have questions, it might be easier to transfer info that way.

Ed
310-809-6038
 
Yeah. You're supposed to be getting stock rings with no oversize, or bore your cylinders and get new pistons too to match the oversize rings.
 
yup oversized rings are too large to use with standard bore and pistons. That's why your having to file them down and why they won't stay on the piston ring grooves when loose.

When you order the rings make sure you are ordering the (STD) size and not the (OS) oversize rings.

12140-47031 PISTON RING SET (STD) | B,C&EC

Not:

12140-47031-050 PISTON RING SET (OS:0.5) | B,N&EC; OS:0.5
12140-47031-100 PISTON RING SET (OS:1.0) | B,N&EC; OS:1.0
 
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where do you guys get our piston rings from? I've bought mine of ebay and that's probably were I went wrong.
 
You stuff oversize rings in a standard bore and the rings are forced into an oval shape. Oversize rings in a standard bore will not give you any compression, thats your problem. Make sure you get proper standard size rings for your engine, you probably wont have to file the end gaps down.
 
They're still available OEM. Looks like G&S Suzuki has 'em for $25/set + S/H.
 
Sorry you have to tear down and purchase new rings.
At least you're on the right path now.
 
chef1366 said:
Sorry you have to tear down and purchase new rings.
At least you're on the right path now.
Click to expand...
yeah for real, with the help of you guys though. see below pics for timing, although I know i need to order new rings.

Top Dead Center
IMG_6693.jpg


Top Dead Center: cylinder 1 & 4
IMG_6696.jpg




Hopefully you can see the markings on the cams. Still Top Dead Center

Exhaust Cam
IMG_6700.jpg


IMG_6701.jpg


IMG_6703.jpg


IMG_6705.jpg


Intake Cam
IMG_6707.jpg


Overall view:
IMG_6708.jpg


IMG_6713.jpg


Here is the view of the exhaust cam dead center on the cam to see how the TDC lines with the markings on the cam to cylinder head.
IMG_6714.jpg
 
Paul's Zuki said:
where do you guys get our piston rings from? I've bought mine of ebay and that's probably were I went wrong.
Click to expand...


anyone bought from powersportsplus.com? I put in the part number that Niclpnut gave me into google and it pulled up their site first for $30.00
 
I think your timing is on OK. Like I said, gssuzuki.com has the OEM rings for $25 per set +S/H, or about $26 each at DeLand Suzuki: both pretty good discount OEM sources.
 
The spacing between the cams looks correct, but isn't the #1 on the exhaust cam one tooth up from the head's top surface? The arrow should be flush?
 
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