78 GS550 engine rebuild

[Jmcb]

I am wondering if I need to do an engine rebuild? The bike seems to starting to run a bit poorly. Some slight pinging at higher speeds, little backfires now and then too. And generally just not sounding great. Ive check ignition timing. It seems ok. But the points are worn down a good amount. I'm fairly certain I can hear the cam chain slinking around when the bike is running aswell. Bad tensioner? Worn guides? Worn chain? Not sure. Admittedly I have not taken the valve cover off to have a look yet. also there's a bit of a rattle coming from the clutch side. Might be a shot bearing or a friend suggested could be the clutch basket is damaged.
I have a whole new transmission. Full clutch gears etc. I have a dyna electronic ignition enroute as well. If I was to strip this engine down over the winter. What would I need out of the gate? Gasket kit obviously. But seal kit and bearing kit too? And where can I buy those? Ive never attempted anything like a full rebuild. So id be in unfamiliar territory..

 

[Nessism]

You might want to try some maintenance: adjust the valves, replace points and condensers, rebuild cam chain tensioner, sync the carbs, etc. Only after all the various maintenance tasks are up to date can you perform a proper assessment as to what might be needed.

BTW, you may want to read through the Newbie Mistakes thread to see how much applies.

Good luck

 

[ChicagoBob]

I agree with Nessism. These are very reliable engines, but respond well to valve adjustment and carb cleaning (with new o-rings in the carbs and intake boots). If your intake boots are shot, new ones are now available at reasonable prices from eBay and Amazon.

The points do wear out over time (but are easy and cheap to service). The 550s were known for clutch rattle when new, and I think the issue was that the clutch basket bolt was not tight enough.

 

[Nessism]

A member here Tkent02 ran his 550 something like 125k miles before the bike was sold. That should tell you right there how tough the engines are. They just need a little maintenance from time to time. It's amazing how many people neglect basic maintenance like valve adjustment until it's too late and the valves/head starts to burn up. Such a waste.

 

[Sam 78 GS750]

I know this one guy who went to the emergency room with severe chest pains. They rushed him into the O.R. and performed open heart surgery, a quadruple bypass... Turns out he just had really bad gas from a burrito he had for lunch.

Ok, so I made that up, but I agree with Nessism and ChicagoBob. Do the basic maintenance first. That may just clear up the issues you're describing. If it doesn't, then diagnose the cause of the symptoms before taking action. I have a sneaking suspicion that a full engine rebuild would be wasted effort on your bike.