Engine Tight when Installing Exhaust Cam

 

1985 GPZ 550. Long story short, sent the bike in to get the carbs rebuilt as they were pouring fuel out the overflow as well as into the cylinders. Carbs rebuilt, and the bike ran great, however, cylinder #4 is completely dead. ZERO compression so it was only running on 3 cylinders. Cams came out to find the retainer or something was wedging an exhaust valve open. Then that part made it's way into the engine, so the head had to come off. They found whoever had the engine apart previously completely butchered cylinder #3 trying to hone it and it looked horrible. We discussed getting honed and re-ringed but the costs for the current repair are already exceeding the value of the bike. Because it ran well before, I said to put it together and we'll look at honing and ringing the engine over winter in a year or two. 
I went to visit the mechanic and every step of the bike is fighting him. This is someone who has been fixing the Jap bikes since the 90's, so he's older and typically grumpy (), anyway, when setting the valves, the engine spins great until he installs the exhaust cam and then the engine is really tight and doesn't want to spin, and that is with 2 caps on. He is not sure why it would be tight, but has anyone every ran into this and figured out the solution, or know what the cause was? I appreciate all your input. Thanks!   

Could be.. incorrect indexing of the cams and the/one valve is pushing against the crown of piston. Don't know the back history but..did You/Mechanic spin the cams in their respective clamped-down cap spots sans any valves installed? This simple effective venue is a tell if machined caps/respective head lowers are correct, also tells if you have a warped head. 

HZ-237 wrote:

I went to visit the mechanic and every step of the bike is fighting him. This is someone who has been fixing the Jap bikes since the 90's, so he's older and typically grumpy (), anyway, when setting the valves, the engine spins great until he installs the exhaust cam and then the engine is really tight and doesn't want to spin, and that is with 2 caps on. He is not sure why it would be tight, but has anyone every ran into this and figured out the solution, or know what the cause was? I appreciate all your input. Thanks!   

Are you saying that he is spinning the motor with only the inlet cam in place and without the tensioner fitted ? if so I would suggest going back to the FSM ref installing camshafts !!!!!

I do not believe they tried spinning it sans valves, but that’s a great idea. I could ask. 

When I was there, they indexed the cams and adjusted the chain on the cams to ensure they were still indexed after the tensioner was installed. But you give a good point where I don’t know how they know it was the exhaust cam causing the issue. I know nothing about mechanics but can’t see how they spun it over with only the exhaust cam installed. 

As for a valve touching the piston, it seems tight throughout the revolution instead of having one tight spot. 

Just a reminder that I know nothing, but could you put the cam in backwards, meaning the lobes for cylinder one are now at cylinder 4?

Did they fit the cam cover after the tensioner ? if so that would cause the motor to be tight throughout the full rotation (there is a chain guide in the cover so it should be fitted with the tensioner released)

If you want to rotate the later series engines with Hyvo chain to check shim clearances/cam timing you need something like these :

 

 

Its maybe only pressing down about 4-6mm but it makes all the difference in the world (first one is mine)
 

I never did see a cam or chain cover/guide. They tightened the cam caps, installed the chain tensioner, then spun the cam to get to the base circle to check clearance. Someone was in the engine before I bought it so would it be possible that the guide could be missing? I don’t recall seeing something like that on the table. 

thank you so much for the replies!!!
 

HZ-237 wrote:

I never did see a cam or chain cover/guide. They tightened the cam caps, installed the chain tensioner, then spun the cam to get to the base circle to check clearance. Someone was in the engine before I bought it so would it be possible that the guide could be missing? I don’t recall seeing something like that on the table. 

thank you so much for the replies!!!

 

The items in injecteds pictures ae "workshop tools" that have been created to simulate the cover being fitted, you aren't "missing" anything. The guide I was referring to is a rubber block in the cover itself. If it was running when you took it into the shop it would suggest the "tightness" has been created by something they have/haven't done. Be careful you don't end up paying for "their mistakes"

A side note. If #3 cylinder liner was a mess, fat chance "honing" would be the cure. And why was that particular iffy to start with? Sounds like you have multiple issues going on. As you mentioned "ran great"...but #4 cylinder wasn't firing? Those spares for the GPZ Unitrack 550 are abundant on ebay, and cheap. Perhaps just source a better cylinder/valves etc.  

Thank you for the replies. Their shop has been around for a very long time and he stands behind his work, so I’m not overly concerned it won’t be right. More concerned it’s being a bear going back together. Just disappointing to purchase a bike with 6,000 miles with an engine that is a mess. 

I’ll have to look on eBay for a liner and see if there’s a good head. I didn’t think it would be easy to find this stuff. 

I really appreciate all the feed back!!!

Unfortunately mileage has no real meaning, 2 miles or 30K. If someone had already been "in there" problems were apparent to some jack-leg before you bought it, SORRY!! 

Totally agree. I honestly don’t think the previous owner even knew it was dug into previously. But, you buy something used, you take your chances. I’m not sure if it could be worse, but it always could be worse. Just looking forward to when it’s all back together and I can get some miles in. Save up for a liner, rings, and maybe a new head and it should be a good bike for years. And I know people who can’t afford new bikes always say this, but right now I’m much happier bringing back an old bike than having a newer one for the same cost……ah, maybe I’d rather have a newer one. 😆