Motor Swap 78 gs400

[khardrunner14]

I need to know what motors bolt right into the 78 gs400 frame. I'm having some issues and for convenience sake I may rebuild another motor and drop it in.

Obviously, another 400 fits, but what else gets in there easily?
- 425?
- 450?
- newer 500 twin?

I'm just looking for a pretty easy transition and I might be able to get ahold of some of these other motors more easily.
Thanks!

 

[hampshirehog]

425 will drop right in. Dunno abot the others.

 

[khardrunner14]

Thanks!

any other ideas on the other motors?

 

[khardrunner14]

bump.......

 

[spots25]

i've currently got a '78GS400 sitting right next to my '01 GS500, so I'll take a look to see if it's feasible. I know the exhaust is different

 

[khardrunner14]

Thanks! I figured I'd have to do exhaust. I'm curious about size and mounting locations.

 

[spots25]

well, I did some looking and measuring, and it seems that it should bolt right up. Everything was too close not to. The only difficulty I see is with the exhaust. The GS500 exhaust comes straight out, on the inside of the wider frame. The GS400 exhaust angles out, on the outside of a narrower frame. The GS500 exhaust would want to go straight through the 400 frame, so it wouldn't fit

 

[SqDancerLynn1]

Might check with www.gstwin.com ? or www.gstwins.com one of those
Maybe you could use your head on a 500 motor

 

[khardrunner14]

Thanks for the heads up on the website...I'll check them out.

As for the exhaust...I wonder if I could weld the two exhausts together...or if there is an aftermarket for the 500 that gives more clearance.

How does the 500 fit into the 400 if the 400 has a narrower frame?

Any ideas with the gs450 motor?

 

[pjm204]

check out www.bikeboneyard.com I think they have a gs400 motor for sale. If not I have a 99 gs500 and a 2001 gs500, as well as a '77 gs400 and a 78 gs400x so I can take some measurements and make sure that swap is feasible. If it is, it shouldn't be difficult to locate a gs500 motor. If the gs500 motor fits then that also means a cr500 motor would fit.

 

[khardrunner14]

Can you check those measurements for me? I need to know about bolt location as well.

Also... since you are not far away what $$ would you want for each of the motors?
- for the 400's I would only need the motor...

- for the 500's I would need motor, starter, exhaust, maybe carbs and electronics

either way check those measurements for me! I'm kind of intrigued by the idea of swapping in the 500...just for fun.

Thanks!!

 

[NEO]

Ive got a GR650 which is a twin. Not sure if it would fit but if it did its a great motor. Sell the whole bike for 200.00 bucks. Needs carbs rebuilt and a starter.

 

[khardrunner14]

It's too big I think. I couldn't get it in the frame. Thanks for the offer though!

 

[jola]

Isn't a 450 just a bored out 400?

 

[khardrunner14]

I think so...I'm just making sure before I throw some $$ at one. I'm looking at all my options.

 

[jola]

I think so...I'm just making sure before I throw some $$ at one. I'm looking at all my options.

That's the smart way. If you want I can snap some close up pictures of my motor and mounts tomorrow (1980 450E).

 

[spots25]

i'm telling ya, unless you can get the 4xx heads on that 500 motor, it won't fit

 

[khardrunner14]

Alright it seems as though 400, 425, and 450 are the way to go. Thanks!

 

[Nessism]

My understanding is that the 425 is a bored out 400 but the 450 is different; uses a plain bearing crank for one thing. Just a word of warning since I don't think it will be a direct bolt-in.

 

[spots25]

i've never looked at one, but I'll bet that 450 motor will fit just fine. If the GS500 motor almost fits except the exhaust, it should go