GT550

Post by **oldjapanesebikes** » Sun Feb 15, 2009 3:12 pm

I bought this 1974 GT550 with the engine locked - it was otherwise complete and too nice to pass up.

Got the head and barrels off today and now know why it was not turning over - I'm sure all those chunks of spare metal are not supposed to be there

The piston had come apart due to (I think) the gudgeon pin snapping - it was cleanly broken into two pieces.

I'll let you know how the rebuild goes.

Post by **Suzsmokeyallan** » Sun Feb 15, 2009 4:39 pm

Ian thats a nice looking bike you got there, so is the big end on that cylinder feeling ok??? what does the top end pin and bearing look like, can you show some pics??

Arne · Post by **Arne** » Sun Feb 15, 2009 5:13 pm

Nice bike! Too bad you'll have to do the bottom end too, but at least you'll know everything is right when you're done with it.

Are you going to do the crank seals when you have it apart? I always think I should do the crank seals when they're apart, but its a bit spendy.

Good luck - Arne

jkevinlilly · Post by **jkevinlilly** » Sun Feb 15, 2009 6:49 pm

Nice on the outside, but not good on the inside. Good luck with rebuild.

Kevin

Post by **oldjapanesebikes** » Sun Feb 15, 2009 7:45 pm

Suzsmokeyallan wrote:Ian thats a nice looking bike you got there, so is the big end on that cylinder feeling ok??? what does the top end pin and bearing look like, can you show some pics??

Thanks Allan.

The big end seems OK, small end likewise appears to be OK which surprises me. The needle roller bearing for the small end is shot - as I mentioned the gudgeon pin was broken into two pieces right in the centre and it appears the small end bearing took a beating as it has a hairline crack and two of the needle rollers have come loose.

All the crankshaft bearings spin freely and feel fine. My only concern is whether I will be able to get all of the little bits and pieces of metal out. I have another crank which I can use, but at the moment I'm thinking I may just clean this one up, replace the small end bearings, gudgeon pins, centre piston, give it a light hone and new rings and see how it looks. There is no sign of scoring in the cylinder wall at all, and while I have a set of first over pistons (thanks again Tim) I prefer to hold off boring unless I have to.

I'll have a better idea later this week.

Post by **oldjapanesebikes** » Sun Feb 15, 2009 7:49 pm

Arne wrote:Nice bike! Too bad you'll have to do the bottom end too, but at least you'll know everything is right when you're done with it.

Are you going to do the crank seals when you have it apart? I always think I should do the crank seals when they're apart, but its a bit spendy.

Good luck - Arne

Thanks Arne - I'll be talking a close look at the seals (at least as best I can - there isn't much clearance to actually look at them) this week and decide whether I'll do a full rebuild. As per my other note to Allan, at least the conrod big ends and crankshaft bearings all feel fine which is good news.

Post by **Suzsmokeyallan** » Sun Feb 15, 2009 9:19 pm

You could clean up everything and inspect into the case as best as possible. If you pour some gas around the edge into the case any stray bits should fall to the bottom, well hopefully anyways. You can then use a large syringe and hose to suck out the majority of the fluid, carefully blowing out the remainder.
Once youve rebuild the top end, done the hone work etc and refit the parts start it up and listen carefully. If its ok then take it for a ride and see how it sounds after about 5-10 mins.
If all is well, then you know, find a nice quiet piece of road to,,,,,,,

Coyote · Post by **Coyote** » Sun Feb 15, 2009 9:49 pm

Way back in the late 70's, I traded some control line model airplanes for a locked up RD250. Pulled the head and found a holed piston and lots of shrapnel. I never even removed the engine from the frame. I took it to work and hung it upside down from a chain hoist on the loading dock. The I used one of those long air nozzles that pull fluid in and mix it with the ejected air. I flushed it for like 10 minutes with air and solvent.
Had it cylinders bored half over, got new pistons and rings a slapped it back together. It turned out to be a great bike. I rode it for a couple of years after that. Then, strapped for cash. I sold it. The guy that bought it wrecked it the first week he had it. From there I think it went to the salvage.
The point is though, all I did was flush it out and all was fine. As Allan pointed out, it's definitely worth a shot - especially if it's a low mileage bike.

H2RICK · Post by **H2RICK** » Mon Feb 16, 2009 12:55 pm

Coyote +1.....although I would make the effort to remove the engine first, Ian. There's a lot more weight to a 550 than there is in an RD!!!

I think you'll probably be able to clean it out quite easily with Coyote's method.....and solvent is pretty cheap anyway. The rest of your plan should see it back on the road toute suite. She's a looker!!! I was always taken with that nice Laredor Red/gold combo back in the day. We sold tons of them....but couldn't give the Hawaii green ones away.

When you get her back on the road, we'll have to go for a spin together.
We'll definitely have the nicest two 550's in Canada!!! Or maybe the ONLY two 550's in Canada.....

PS: If you need some head gaskets just PM me and we'll make a deal. I scored a bunch of 'em off fleabay before they went overboard with all their changes.

Post by **oldjapanesebikes** » Mon Feb 16, 2009 3:18 pm

Many thanks for the suggestions and input folks ! I'll let you know how it goes.

Post by **Suzsmokeyallan** » Mon Feb 16, 2009 3:51 pm

Honestly turning the bike upside down and spraying our the case would be a good idea, but not for the meek of heart. Thats a lot of weight to be turning upside down so you gotta be careful it doesnt slip or drop.
If you know someone with a forklift and some slings nearby to you thats even better.
Sorry to say Rick, you two are NOT the only ones in Calgary with GT550s, theres a black one thats lurks along the 1A to Cochrane, so i know theres at least three now.

Coyote · Post by **Coyote** » Mon Feb 16, 2009 8:13 pm

No prob Allan. it was a 2 ton hoist with the tranverse beam being about 15 feet up. I used 2 slings and a short loop of chain - through the sling hoops and onto the hoist hook. I cqan say though that I got my a** covered in solvent and could hardly wait to get home and in the shower.
But HEY, it's the labor of love. Right?

Post by **oldjapanesebikes** » Fri Apr 03, 2009 9:44 am

Just an update - turns out that removing the engine and doing a full disassembly was the right way to go. In addition to the piston issue, when I pulled off the clutch basket, the starter clutch assembly basically fall apart in my hands as the centre boss had come completely apart. In the photo below you can see the broken one to the left, and what it's supposed to look like to the right.

I suspect a few folks on this board would be aware that Suzuki completely redesigned the starter clutch assembly in 1975, the year after my bike was built and obviously the updated version had never been installed. The service bulletin which details the changes and new part numbers is GT-26, dated August 15, 1975 and a copy can be found here. I had two 'good' old style starter clutch assemblies from the donor bikes as neither of them had been updated either, but I wasn't too happy with doing this as I could reasonably expect the same failure mode again at some point - and as I was putting this on the road for my wife, I know she would not be impressed if the starter quit working !

I managed to track the new style starter clutch assembly down from the UK based Suzuki-Dave from whom I've bought other items previously. Tracking down all the other seals I needed has taken some time, as some have not been available from Suzuki for quite a while - for example the oil seal that goes behind the drive sprocket ( 09283-25050 ) I finally sourced from a dealer in New Zealand, and most of the bearings used for the crankshaft and the con rods are no longer available from Suzuki either. A couple of the o-rings are odd sizes, and no longer available, but I have managed to find sizes that seem to fit OK from Hi-Tech Seals here in Calgary..

The photo below shows the new clutch assembly to the left, and the old style to the right - quite a difference.

I now have the engine back together, and will be putting it back into the frame in the next few days. I will be installing a Boyer-Bransden ignition system and fixing a few other minor things, and then if the snow ever stops (it is snowing again right now as I'm writing this) we will see if it actually runs !

H2RICK · Post by **H2RICK** » Fri Apr 03, 2009 10:58 am

Ian, that's quite a story of how you tracked down the bits for the updated clutch assembly. Those folks at Hi-tech are very useful and helpful. The old bike resto hobby in Calgary would be a lot harder without them, IMO.
There really is nothing wrong with the original starter clutch design which has been used on countless other Japanese bikes since the dawn of time, however......
What PROBABLY causes the premature failure is poor engine tuning or other types of problems like that. The owner grinds and grinds the engine over with the starter instead of fixing the problem and eventually the starter clutch craters in disgust. Poor choice of tranny fluid won't help, either.
Glad to hear your 550 is on the road to full health. Now, if it EVER stops flippin' snowing, we might finally get out to A & W for a ride together. Next week is shaping up nicely....if we can survive this weekend. Grrrr......stupid weather.....Grrrrr.....

Post by **oldjapanesebikes** » Tue Apr 07, 2009 11:32 pm

Just an update - it runs !

The plan it to take it for a short ride tomorrow just to see what else still needs to be sorted.

GT550

GT550

Thanks !