GS450 Low Compression after rebuild

[tkent02]

Why would you grind those?

 

[gearhead13]

I use a wire brush on a drill to clean the fronts and backs of valves, cleaning the front(top) helps the suction cup hold better. You need to lap the valves until you see a nice smooth sealing surface around the entire seat and valve circumference. A little flashlight and magnifying glass works well to inspect them.

 

[JRHemmen]

Why would you grind those?

What gearhead said. I ended up not using the suction tool and I used a drill with a hose attached to the drill and valve. I know this is frowned upon, but I went at a slow speed and switched directions often and I think they look pretty good. Tomorrow I'll rent the spring compressor and try to get it all back together.

 

[tkent02]

Frowned upon, but it works just fine.

 

[mottacycle]

The bike was unable to start in its current condition. I'm sure the valves are leaking, but I think the timing should have been fine. Now I'm taking it apart to lap the valves and make sure the timing is right. Hopefully after this I'll be able to actually start it.

fine grit lap compound and clean clean clean meaning wipe off check, then clean with carb cleaner then reapply more, use a light in the ports (in and ex) to check for fit.. the way i do it.... also by hand is the best no drill attachments they willl give u more problems with high and low spots just my exp.. just posted didnt realize u already went the drill bit way opps..... good luck

 

[jdvorchak]

If the tool sticks ok than not needed but preferred. You can't have them too clean. Also if you have carbon build up on the pistons it won't hurt to wire brush them as well. Looks like you're getting close. Would like to have seen a before pic to see if they were bad enough to leak badly. But the seats don't look burned. How is the head gasket? I still can't believe you got 40 and 70 pounds compression. For those kinds of numbers you'd have to have a blown head gasket or a burnt or misadjusted valve and those valves don't look like they are flame etched.

 

[jdvorchak]

Are the cylinder walls scored? Post some pics of everything you're seeing with the heads off.

 

[JRHemmen]

Would like to have seen a before pic to see if they were bad enough to leak badly. But the seats don't look burned.

Heres the exhaust valve from the cylinder putting out 40 PSI. My guess is that my timing was off, because the valves didn't look that bad and I have a brand new head gasket.

John, I'll post a picture of the cylinder walls in a bit, I'm headed out to get the spring compressor now.

 

[JRHemmen]

On a different note, (maybe this has something to do with my poor compression), It looks like something has condensed or leaked all over the head, and its starting to take my new paint off with it when I wipe it away. Its all the way around the cam cover gasket, so I'm wondering if its the oil that I rubbed on that gasket before putting it on. However, it's also in random spots on the head, specifically in the low spots on the sides where the spark plugs screw in. I'll try to post a picture of that later.

 

[jdvorchak]

Agree that valve and seat don't look bad at all for 40 lbs. I am really starting to doubt that it is really 40 lbs. I have seen more than once a guy with low numbers borrow another tester and like magic that 40 or 50 becomes 120.

I have two compression checkers. One an old MAC tools and a new Harbor Freight. I bought the HF unit because it was like $19 and the proper adapter for my old MAC, to fit motorcycle spark plug holes, was about $12. Both of those read within 10 lbs of each other. But I also have one of those old units with the rubber cone on the plug end and you are supposed to hold it into the spark plug hole. I found one of my sons checking compression on a Chevy with it and complained to me he was only getting about 80 lbs compression. I then used the MAC and like magic he had 130 lbs. And the leak down test showed he had ok, not good, sealing. His complaint was burning oil and it turns out the valve stem seals were shot. The 130 number came from the engine having 230 K miles and was getting tired.

 

[JRHemmen]

I just finished putting all the valves back in. When I went to put the head back on, I realized that I hadn't put the 2 little dowels back in the first time, maybe that was part of the problem. I took pictures of the cylinders as well.

 

[londonboards]

I don't want to be a miserable bastard or stop anyone from having any fun but it seems to me that your knowledge of bike engines and basic mechanics at this point in time is so lacking that you should really stop this project before too much more damage is done. I really don't mean to be rude but honestly is the best policy here.

This is what I recommend. Spend some time reading up about valve trains, springs, pistons, engines and general bike stuff. Start here: http://members.dslextreme.com/users/bikecliff/. There are all kinds of articles there that will help you with valve lapping and the like.

Try to find a GSR member near to you who is willing to spend a couple of hours with you looking into your engine. Honestly, stuff like cam chain timing and the like are hard enough to understand for guys who have been ripping these engines apart for over 20 years.

It is so difficult for any of us to help you on a forum like this when we know nothing about your level of experience with these things. It just seems that from what you have written that you are in danger of making things worse because you really don't know what you are doing.

The 2 most obvious ones to me are; you need to hold the throttle wide open when you are doing compression testing (it will tell you this if you read anything about compression testing or look at any YouTube vid) and secondly you left the collets out when you re-assembled the valves and springs. Without the collets ("little dowels" as you call them) the valve will not close at all. I'm guessing you might just get a 40psi reading even if all your valves were stuck open.

The other thing is that cylinder wall does not look good to me. You need to get this checked physically by someone that knows.

I just think you ought to get someone over to take and look at your motor whilst it's apart. Get some help from someone. There is only so much we can do by remote from here.

I want you to get that bike back on the road and for it to be safe a reliable and right now I don't think we are going the right way about it.

 

[JRHemmen]

I don't want to be a miserable bastard or stop anyone from having any fun but it seems to me that your knowledge of bike engines and basic mechanics at this point in time is so lacking that you should really stop this project before too much more damage is done. I really don't mean to be rude but honestly is the best policy here.

This is what I recommend. Spend some time reading up about valve trains, springs, pistons, engines and general bike stuff. Start here: http://members.dslextreme.com/users/bikecliff/. There are all kinds of articles there that will help you with valve lapping and the like.

Try to find a GSR member near to you who is willing to spend a couple of hours with you looking into your engine. Honestly, stuff like cam chain timing and the like are hard enough to understand for guys who have been ripping these engines apart for over 20 years.

It is so difficult for any of us to help you on a forum like this when we know nothing about your level of experience with these things. It just seems that from what you have written that you are in danger of making things worse because you really don't know what you are doing.

The 2 most obvious ones to me are; you need to hold the throttle wide open when you are doing compression testing (it will tell you this if you read anything about compression testing or look at any YouTube vid) and secondly you left the collets out when you re-assembled the valves and springs. Without the collets ("little dowels" as you call them) the valve will not close at all. I'm guessing you might just get a 40psi reading even if all your valves were stuck open.

The other thing is that cylinder wall does not look good to me. You need to get this checked physically by someone that knows.

I just think you ought to get someone over to take and look at your motor whilst it's apart. Get some help from someone. There is only so much we can do by remote from here.

I want you to get that bike back on the road and for it to be safe a reliable and right now I don't think we are going the right way about it.

I appreciate the concern. I am new to mechanics, and I planned for this bike to be how I learn. I wasn't referring to the keepers, those are all in place correctly. I meant the hollow tubes that go between the head and the jugs, approx. 1cm in diameter and 2cm long.

I admit I didn't do any reading on compression testing, I went by what the worker at autozone told me, which included nothing about the throttle. I've certainly been anxious about getting the bike running, but I'm trying and will continue to try to keep that from interfering with the quality of my work. I extensively read through the bikecliff site as well.

 

[gs45082]

I might hesitate to go as far as Richard, but stepping back and doing a little reading before tearing into a motor for a second time might pay some serious dividends in saving you time and money, not to mention reducing potential for damaging your motor. We all want you to have a safe, fun bike; and as a fellow 450 owner I can tell you it's worth the frustration when it all comes together and you're tearing down some good roads. You have an amazing little machine waiting on the other side of all this work.

First thing first, do you have a manual? I mean an actual paper book. YouTube and the forums certainly have their place you're not getting very far without a manual. I got this one off amazon and it's been great: http://www.amazon.com/gp/product/0892872373?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00

As indicated, your bores look quite rough. But not seeing them in person makes this a tricky call. If you drag your fingernail nail across any of the gouges, do you feel it hanging? With all the other unknowns flying around, I'd probably just put it all back together (correctly this time!!!), and see what your compression reads. And get a wet reading too by squirting a little oil in the plug holes, if compression increases by a large margin (15-20 psi increase??) then yes you need a ring job. Buuuuut even in that case, you probably have enough compression to get her running, at least to see if everything else is in good enough shape to justify the ring job.

 

[JRHemmen]

I just ordered that manual, thanks. I looked over the cylinders, and had someone else look over them, and they both seemed fine. I think it's just some kind of stain in the picture, because they feel totally smooth when running a fingernail over them.

 

[tkent02]

I took pictures of the cylinders as well.

These cylinders are wasted from sitting with water in the bores, that's rust in a nice straight line because thats where the piston rings were. Rings are probably toast too. Easy fix, replace the cylinder, pistons and rings with Ebay stuff. However, that same water also likely ruined things down inside the engine as well. You probably have rust on all kinds of stuff down inside there. I bet if you were to pull the pan off the bottom of the engine that water would still be in there. Take a look.

 

[JRHemmen]

These cylinders are wasted from sitting with water in the bores, that's rust in a nice straight line because thats where the piston rings were. Rings are probably toast too. Easy fix, replace the cylinder, pistons and rings with Ebay stuff. However, that same water also likely ruined things down inside the engine as well. You probably have rust on all kinds of stuff down inside there. I bet if you were to pull the pan off the bottom of the engine that water would still be in there. Take a look.

I have pictures of the pan in my build thread, I didn't see rust on anything when I had it all apart. How would water have gotten in there, condensation? The bike was stored inside at the POs, and at my home as well.

 

[tkent02]

Maybe some previous owner left it outside with a spark plug out or maybe with the carburetors off. Could have been a long time ago. Not sure, but I've seen it before, it's rust.

 

[JRHemmen]

Do these pistons and rings look acceptable? Also, is there any way I could clean the cylinders out without buying new ones?

https://www.ebay.com/ulk/itm/400656792028

 

[gearhead13]

The best way would be to buy new rings and hone the cylinders. I doubt there is anything wrong with the pistons, but the rings are an unknown. Depending on the mileage on the engine, maybe just a light hone job with the current rings would suffice.