New Rider and Bike in Washington DC '79 Suzuki

S

szlaughlin

New Member
Hi everyone,

Just got my first Cafe Racer- 1979 Suzuki GS425 I will be needing help with advice and opinions- mostly Cafe'd out but needs a little work. As cool as the brushed steel looks, its rougher than it is in the pictures and will need paint. There is some mechanical sorting to be done as well.

If anyone has any ideas let me know. I'm trying to source a short rear fender so let me know if you have anything or have an idea of what to use.

Also, the bike is having some (I think carburetor issues) throttle application (in neutral or in gear) results in a dip in power, almost to the point where the engine cuts out, then slow buildup and eventually the desired power output. Basically there is significant throttle lag and no linear power delivery. Any ideas? The bike has been sitting for a month (according to the seller), but starts right up.

There is also a strange sparking coming from a screw recessed in front of the gas tank under hard throttle application. It's pretty concerning considering the sparks are near the gas tank. And the Rear tailight just stopped working after hard throttle application too. Brake light still works though. Whats going on?

Anyway, here it is:

P1014642.jpg


IMG_0299.jpg
 
Really awesome potential here! So many great things about this bike.....

I know you said the bare metal is rough.... Look into buffing it out. It's a timely process, but it would look SWEET, and you're over half way there! Just a thought. The carbs are your issue with the lag at launch. If I'm seeing it correctly, you've got no air filters on those carbs, just some sort of bent hose thingie, right? If you run without an air filter, this changes the mixture of air/fuel. Fixable, and you will be a carb expert when you're through. Take your time and do your research on it. Also, I'd recommend at least some sort of a filter, if you ride this thing more than a few miles on the weekend. Dirty carbs = rough running motor.

Sparks you say? Yeah, that's bad. The electrical systems are the toughest things about most older bikes. Pull your tank, look for clues... Sparks would leave some sort of carbon residue somewhere. If it's arcing off your tank, look for the marks under your tank, then find the bolt or (more likely) the electrical connection that is not insulated properly. Electrical tape is not a sufficient fix. If the wire is hard and brittle, it's worth replacing. It will fail when you are as far away from your tool bench as possible, I can assure you of that! ;D Your coils are under that tank, so keep in mind, sparks coming from that could be a dangerous thing!

Get yourself over to the gs resources dot com and look for wiring diagrams. Read The Stator Papers over there, too. Also, if you don't have the Clymers manual for this bike yet, find one and read it. A must have for the bench.

The tail light could be just a bulb or a loose connection. Since you have no idea of the skill level of the PO, pull your tank and seat and start looking for bad wiring connections. Chances are you'll find out a few things.

This is gonna be a great looking bike when you're done. It's nice to see a Suzuki twin on here.

loudest143
former GS owner.
 
That's an awesome bike so far. I agree with everything Loudest said, but I'd like add that a good cleaning while you're working on the carbs couldn't hurt. If the intakes have been more or less open, some gunk could have already gotten in there.

And on the wiring, while it is likely the most frustrating part of these old bikes, you can at least take some solace in the fact that overall they're still pretty simple. I'd imagine that can be completely rewired from scratch over the course of a day if you've got the proper wiring diagram. Yours should be a bit easier than stock because you're not running signals. Just imagine if it was a modern bike with computers, fuel injection, etc. I had to rewire my bike (having never done it before) and got it done over the course of a Saturday.

+1 on cleaning up the finish over painting, but that's a matter of preference. What ever you decide to do, you're starting off with a cool bike.

Welcome to the site.
 
Thanks for the responses,

The throttle problem has been getting better! I think after a few rides, the fuel circulation has cleaned alot of the parts. All I really plan on doing at this point is cleaning the carbs and syncing them. If there is still a problem i will rebuild them. Worst case, any replacement carbs available to replace Mikuni BS34's? I have the clymers manual.

As far as the bare metal... There are a few dents in the tank and the corrosion is killing it. And I've always wanted a bike in shelby blue with a white racing stripe ;D

Any Thoughts on a rear fender?
 
The only carbs i can think of are vm30's. But you will need a new throttle cable, manual choke setup, mounting flanges, etc. Have you had the carbs off yet to. lean them?

Nice bike btw.
 
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