Replacement engine possibilites for '78 GS 550E

[zanza14x]

Hello all again,

I found out that after only 20,000 miles, my 1978 GS 550 engine has called it quits. Has one dead cylinder, and the others are not in much better shape, including much burning oil, etc. Of course, it could possibly be rebuild, but I have been told by many people that if I really want to keep it, (which I really do), I would be better off finding an engine that would work for it and swapping that in. I have been told that a 650 of approximately the same year might be compatible, but I am not sure what years or other engine sizes might work besides 1978? This engine does have the points ignition system as well. I realize that engine swap questions are not encouraged, but this determines the life or death of an otherwise quite nice GS. Any incite would be much appreciated. Thank you.

[Nessism]

20k miles on a GS engine is nothing unless it's been abused by lack of maintenance.

One question is whether you are capable of rebuilding an engine? If so, I'd tear down the one you have and check all the parts like the valves and the cylinder/pistons. Most of the time a GS engine can be freshened up with new rings, a valve lap job, and new gaskets/seals. You can purchase a used engine for a similar price to rebuilding but I'd trust an engine with rebuilt top end over a unknown used engine which could spring a head gasket leak or worse.

[BassCliff]

Hi,

I agree with Mr. Nessism's insight. Have you done a compression test?


Thank you for your indulgence,

BassCliff

[SqDancerLynn1]

What is the history of the motor ??? Last time the valves were adjusted ?

[zanza14x]

I do not know the exact history of the bike, but knowing the previous owner somewhat, I am sure it underwent extensive abuse and neglect. Just about everything on the bike has been gone over since I got it a little over a year ago, but I believe we only did a quick/minor engine checkup. I know a couple people who are very knowledgeable about motorcycles who have been guiding me. The compression is (1-4) 55, 60, 0, 60, which I know, besides the dead hole, is much too low for any motorcycle. One of my contacts has informed me that since it is also burning oil out of either 3 or 4, more than likely 3 looking at the plug and the compression, along with the dead hole, that there is either a bent or "shot" valve, or a hole in the piston. To be honest, we simply do not think this is the rings or gaskets having gone out. They may have after the matter of fact, but not the major problem. My contact said he should be able to get a small camera to see inside and see what is really wrong, without having to tear it all apart. Also, most people have told me that I should just scrap the bike, cut my loses, and move on. I simply do not want to do this. The thing is, is that from what I have heard, an engine rebuild would cost significantly more than finding a replacement motor, and it would be much more simple to swap engines. Granted, a rebuild would be much more preferable, but I simply do not know if I can afford to do so. Besides the swappable engine sizes and any other info, if someone could direct me to a site or place where I could find quality rebuild parts for a "decent" price (i.e. valves, pistons, etc., etc.), then maybe I could rethink things. The bike looks like hell, but I would love to keep it on the road for years to come. Thanks.

[Nessism]

You are getting way ahead of yourself and won't know what needs to be done until you inspect everything properly. Pull the head and cylinder off, pull the valves out of the head and inspect the parts. If the cylinder is worn or the head is damaged beyond normal limits, go to plan B and look for an engine.

[zanza14x]

Alright. I took the engine apart, removing the head, etc. There is about a .5" hole in the #3 piston and it appears that the #3 intake valve is shot. We tested it by pouring gas through both the intake and exhaust manifolds as advised and it leaked both times. Otherwise, besides the fact that all new gaskets wouldn't hurt anything, I believe those are the main problems. Now, the question would be to replace the parts, or the whole thing? As mentioned, I do not have overflowing funds, but I do not want to be too cheap if possible... Also, where would the best place to buy what I need? Any other info would be appreciated. Thanks.

[Larry D]

Dude.... we need some pictures of that !!!

If it were me...I'd start looking around for a 550 engine to replace it. No need trying to cobble in a completely different engine.

[waterman]

IMHO, your best bet is to purchase a replacement engine, specifically, a 78 to 80 550. With the holed piston, it would be questionable to sink more money into it since the damage may be more extensive than you think. Even with what you have described, to rebuild it will require new rings, piston or possibly set of pistons, valves and/or head, gaskets, and then you still don't know what other damage may have occurred from the abuse. Rings and gaskets are going to run near $200. Used pistons and valves are almost always available on ebay or from members here.

Check around and see if you can find a bike junk yard in your area, used 550 motors should be easy enough to find, they made a bunch of them. I would stay with early style, 77 to 80 I believe so you can simply swap it out. The later models used CV carbs and will require different carbs than your VM style.

Might also check craigslist for another complete bike, 550 were plentiful and can be had cheap.

Forget the 650 option, they all used CV carbs and most of the 650 were shaft drive anyway.

[cowboyup3371]

I faced a similar issue when I first got my bike but have since found out it wasn't nearly as bad as first thought. However, while stressing over it I found a place on the east coast that rebuilds motors and sells them for a fairly reasonable price. Check out this site and see if they might be able to help you.

http://www.drumhillcycle.com/

[zanza14x]

Hi all. Thanks again for the advice. I can post pictures hopefully some time tomorrow, we took quite a few. I have been searching ebay and craigslist pretty regularly, but nothing all that local that I would consider. Keep the advice coming!