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GS450 Low Compression after rebuild

  • Thread starter Thread starter JRHemmen
  • Start date Start date
Phew. Glad it isn't something more serious. When I put the chain tensioner back in, we didn't loosten any bolt, I turned the spring fully counter clockwise allowing the plunger to depress and held the spring out until it was bolted into the engine. Is this acceptable, or do I need to redo it? Also, what would cause the choke to be stuck? I did a full carb clean and installed new jets and O rings as well. Do I need to take it apart and spray out the passages again?

Thanks again to everyone for the tremendous amount of help you've been. I'm looking forward to the day where I'll be of some benefit to others on the forum once I know more about these bikes.
 
You need to understand how this works. The screw holds the plunger back so you can install it. Holding the spring all the way back does the same thing. For the tensioner to work the screw needs to be loose, and locked in the loose position. If you could move the plunger easily it sounds like it's in the proper unlocked position, but I'd still check it to make sure. You certainly did it the hard way.
 
That certainly seems to be how I go about things, haha. I read through the first 60 pages of the manual tonight and I already have a much better understanding than I did 24 hours ago. Is it possible that a spark leak could cause my backfire? I'm not sure what the proper terminology is, but if my spark plug boots are in pretty bad shape (easily pull right off coil wires), could there be some arc that causes a delay in ignition? I'm hesitant to think it's that since it was definitely a backfire through the carb, and not an after fire (out the tail pipe), but I don't want to rule it out just yet.
 
Going about things the hard way? Or just generally being un/misinformed? Sorry.
 
My new sealed rings arrived in the mail today, they're rusty. Is this okay? I'm hoping I can just sand the rust off?
 
I've used 1500 grit sandpaper on a really flat surface to knock the rusty spots down to level with the surface and not worried about it. Just make sure that the ring isn't tight in the groove.

I'm somewhat concerned that the rings may not be the right size. As I recall, the top ring is 2.6mm wide and the second ring is 3.0. There appears to be more than .4mm difference between these rings. Have you checked them against the originals? The thickness is 1.8mm for both as I recall.

The end gap - free -should be about 8 - 9mm and these top rings look to be more like 3mm. The top ring looks to be highly questionable to me.

If they are the same then disregard my comments.
 
John Park said:
I've used 1500 grit sandpaper on a really flat surface to knock the rusty spots down to level with the surface and not worried about it. Just make sure that the ring isn't tight in the groove.

I'm somewhat concerned that the rings may not be the right size. As I recall, the top ring is 2.6mm wide and the second ring is 3.0. There appears to be more than .4mm difference between these rings. Have you checked them against the originals? The thickness is 1.8mm for both as I recall.

The end gap - free -should be about 8 - 9mm and these top rings look to be more like 3mm. The top ring looks to be highly questionable to me.

If they are the same then disregard my comments.
Click to expand...

I haven't checked against originals, I haven't been home yet and I was hoping to leave the engine alone until I had my frame and electrical finished. I'll try the sandpaper method, thanks. I think the difference is just due to the camera on my phone, when I hold one over the other .6mm definitely seems like a plausible number for the size difference between the two. I'll check with calipers tonight.

They are P/N 12140-44110-100.
 
I bet that rust will come off with a rag and some oil or something, sanding shouldn't be necessary.
 
Those are 1mm over rings, cannot use those on stock bore cylinders and pistons
 
I assume that's what the -100 means on the part number? Do I need -000?
 
JRHemmen said:
I assume that's what the -100 means on the part number? Do I need -000?
Click to expand...

Now I see; the two thinner rings are the oil control and the other two are top and second. Without the spacer ring I wasn't thinking of them. However, the part number I see is 12140-44110 for standard rings. 12140-441100- 050 is .5mm oversize and 12140-44110-100 is 1mm oversize. While 000 may make sense, it's redundant; it's just a suffix.
 
Okay, thanks. I didn't include the spacer in the picture because it didn't have any corrosion on it. I'll return these and buy the right rings.
 
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