Bandits '77 GS750 Revival

[93Bandit]

After sleeping on it, I recall it was difficult to start when hot, it would crank a while before finally firing and it would stumble quite a bit. When I gave it a little choke, it fired right up so that makes me think I have the pilot jets too lean. They're 1 turn out, but maybe they should be 1.5 or so. I'll turn them out a little more and then see if that helps the idle air screw adjustment.

Also, I didn't adjust the slides at all, they're at the factory setting. Figured they'd be fine where they are, but the bike has 18k miles so it's probably due for a balance. I'll try these few things and see what happens.

On a side note, after running it a while I noticed a substantial amount of smoke coming from the head at cylinder 1. The engine is oily everywhere, but especially there. It never burned off and stopped smoking so the head gasket is likely leaking faster than I expected. A full rebuild will be necessary sooner than expected. I won't have the time to get into it that deep this year since baby #2 is due in April. Maybe that'll be next winters project.

 

[allojohn]

A vacuum sync will make a massive improvement... beg, borrow or steal a Morgan carbtune. 1 turn out on the fuel is right, air jets should be half a turn either side of 2 turns out - and each jet could be different.

 

[93Bandit]

Thanks for the info. I thought I had read the air screws would be ~2 turns out. I'll have to double check.

I actually have a Morgan carbtune, recently purchased it. Haven't had the chance to use it yet but this will be a good excuse. I'll try to balance the carbs next, then maybe fiddle with the pilot and air jets again if needed.

 

[93Bandit]

So we had one good 58 degree day and now it's cold again. I'm getting impatient and can't run the bike outside to tune the carbs because it's so cold. So, I've had an idea for a while now and finally decided to try it.

The previous owners of the house were growing the devils lettuce in the garage and they put a fan in the wall of the garage that blows out. I was trying to think of a way to use it until I take it down and patch the hole. I repair a lot of small engines in my garage and always wish I had a place to run them in the winter months since it gets so cold here. I've ran stuff inside for short periods of time, but never long enough to get to operating temp and tune. I bought some ducting and some dryer vent hose. I used the regular flexible vent hose (rated for 180F) from the fan to the Y section, and the more rigid vent hose from the Y to the exhausts (rated for 450F). So far it's working really well. I ran the bike up to operating temp and the hoses never got too hot to touch and the garage didn't smell like exhaust at all. So I think it'll work out well enough for small engine stuff. Hopefully it holds up over time.

 

[eil]

That's a fascinating way to do it. I gotta keep that in mind.

 

[93Bandit]

That's a fascinating way to do it. I gotta keep that in mind.

Where are you at it SE MI?

 

[Grimly]

So we had one good 58 degree day and now it's cold again. I'm getting impatient and can't run the bike outside to tune the carbs because it's so cold. So, I've had an idea for a while now and finally decided to try it.

The previous owners of the house were growing the devils lettuce in the garage and they put a fan in the wall of the garage that blows out. I was trying to think of a way to use it until I take it down and patch the hole. I repair a lot of small engines in my garage and always wish I had a place to run them in the winter months since it gets so cold here. I've ran stuff inside for short periods of time, but never long enough to get to operating temp and tune. I bought some ducting and some dryer vent hose. I used the regular flexible vent hose (rated for 180F) from the fan to the Y section, and the more rigid vent hose from the Y to the exhausts (rated for 450F). So far it's working really well. I ran the bike up to operating temp and the hoses never got too hot to touch and the garage didn't smell like exhaust at all. So I think it'll work out well enough for small engine stuff. Hopefully it holds up over time.

Excellent. I'd bought the fan (and no lettuce) but never got the hose. Commerical exhaust hose for vehicle workshops is extortionate, and I didn't know if the dryer hose was up to it..

 

[93Bandit]

Excellent. I'd bought the fan (and no lettuce) but never got the hose. Commerical exhaust hose for vehicle workshops is extortionate, and I didn't know if the dryer hose was up to it..

I was looking into the commercial hose but as you said, prices are ridiculous. I figured I could buy a lot of dryer vent hose for the same price if it needs periodic replacing.

The "regular" foil type vent hose probably isn't up to the task if connected directly to the exhaust pipes since it's only rated for 180F which is why I chose to use the more durable and rigid hose to attach directly to the exhausts, which is rated for 450F. I figured as long as the majority of it's use is while the engine is idling, it should be OK. The hose is 4" and it just fits over the 750 mufflers. It's snug on the end of the muffler since it has an OD of 4" as well, but the exhaust size tapers down and I have the hoses pushed over as much of the pipe as possible in an attempt to create an airgap between the exhaust and the hose. The idea is that this will draw in ambient air as well which hopefully helps cool the exhaust gases. I also figured by the time it gets to the flexible foil hose, it has cooled enough to not harm the hose. As I mentioned before, I could touch the hose without burning my hands even after it was nearly operating temp. Definitely cool enough once it gets to the fan.

The hose routing needs to be redone to get rid of those few sharp 90 turns which will hopefully help the flow. I just set it up as is as proof of concept. The first test run far surpassed my expectations so I will move forward with refining it as needed.

One downside already is that my 850L exhaust pipes are larger than 4" diameter so as it current sits, I cannot hook up my 850. I will probably make some cone type adapters in the future for other exhaust shapes. This would probably be ideal anyways as it would be larger diameter than the exhaust and slide over with minimal contact, increasing the air gap and ideally the cooling affect.

For those who may want to replicate this, I can get a detailed parts list if you want. I believe I have about $70 in parts. The only thing I don't know is the CFM of the fan. It was installed in the house when we bought the place and I couldn't see any markings on it. But the inlet is 6" diameter, overall diameter is probably ~14" and it's all metal. Cast aluminum housing and the cage inside is metal.

Here's a quick video of it all running (click the image below). Tried to get a longer video but was limited by file size. I'll try to get a better one in the future.

 

[Grimly]

That's excellent. Of course, different markets have differing things available, but I do have about 20ft of 5" flexible stainless steel flue to make the ends from. The long ducting piece I can find something for.
This what I've got as a fan - a bouncy castle centrifugal blower. Handily it has a flange face on the intake to allow fitment of /whatever/.

By the time the exhaust gases reach it, they'll be quite cool.
It shifts a lot of air, but is a noisy bugger, so I'll mount it upstairs to keep the noise as far away as possible and drop pipes from the ceiling.
A similar system bought in would cost many hundreds or a couple of thousand.

 

[93Bandit]

That fan looks like it's up to the task for sure! 5" pipe would be ideal I think. It would allow for more ambient air to be drawn in around the tail pipes which will help cool.

 

[93Bandit]

Been too busy to work on the 750 but it was 55 and sunny today so I decided to see if it would run better in the warmer weather. Went around the block and It definitely ran better, pulls really well but still has an erratic idle.

I did solve the random hanging idle though. The spring on the idle adjustment screw was broken so it wasn't keeping tension on the screw, so engine vibrations would slowly screw it in, increasing engine rpm. Robbed a spring off a spare set of carbs I have and that seems to have fixed that issue. Nothing ground breaking but it's progress.

 

[93Bandit]

My wife and kids left me home alone yesterday, and it was beautiful weather so I decided to spend the day in the garage. Finished up some smaller projects I had going and then got to work on the 750.

For starters I rebuilt the petcock with a K&L rebuild kit I ordered from Ebay. As I understand it, not many guys here have had success rebuilding their petcocks, but the only other option I have is a china made one so I decided to try my luck with rebuilding the OEM one. I disassembled it and thoroughly cleaned it. then I polished all the sealing surfaces with 0000 steel wool. I made sure to get way down into the port where the vacuum valve opens/closes for fuel flow. It was a crusty and had some o-ring material fused to the sealing surface. I spent quite a bit of time lightly scrubbing with steel wool. I used a pencil to push the steel wool into that tapered hole. Eventually I got the inside polished well enough, put a light coat of silicon grease on all the rubber except the vac diaphragm, and got it all put back together. Then I realized I didn't take any pictures for you guys! Sorry, maybe next time... So far the petcock is holding, no fuel leaks yet. We'll see how it holds up over time.

Next, I synched the carbs. Below is a picture of the bike setup with my aux fuel tank, carb tune, and fan.



Here's a picture of the carb tune after first hooking it up. You can see the carbs are way off from each other.



And here's as close as I could get them. This is the first time I've balanced carbs, so I don't know if this is close enough or not? I fiddled with them for a while and this is the best I could get. Unfortunately the idle is still somewhat erratic, unsure why... I'll post a video of it idling, maybe later today.



What do you guys think, did I get them close enough or should I balance them again?

Against better judgement, after balancing the carbs I decided to go for a shakedown ride to see how it's running. Ended up going 75 miles and it ran well. Engine sounds smooth and strong all through the revs, except for the erratic idle, grrr...

During this ride I observed a few things. It seems like the forks are twisted a little to the right. I thought the handle bars were bent, but after looking at the triple clamp you can tell it's turn to the right ever so slightly. I'm unsure if this can be corrected with an adjustment, or if my tubes are bent?

Also it desperately needs tires. I should not have ridden it that far on those tires, I'm pretty sure they're from 2005...

Lastly, due to the bad tires and overall unfamiliarity with the machine, I never went WOT in 1-3rd, but I did roll into it pretty hard a few times. Wow, this thing feels much faster than my 850. I don't know if it's just me or what, but I think I'm going to love riding this thing.

 

[93Bandit]

Went for another ride today on the bike. Decided to try the kick starter and she fired first kick. Nice. However, odd coincidence that after using the kick once the starter no longer works. Just the "click" of the starter solenoid. Ugh...

 

[Grimly]

Went for another ride today on the bike. Decided to try the kick starter and she fired first kick. Nice. However, odd coincidence that after using the kick once the starter no longer works. Just the "click" of the starter solenoid. Ugh...

I doubt there's any relationship. The starter turns the LH end of the crankshaft, while the kicker turns the right end via some gears.
It's just another curve ball sent by the Small Suzuki Gods to melt your head.

 

[93Bandit]

I doubt there's any relationship. The starter turns the LH end of the crankshaft, while the kicker turns the right end via some gears.
It's just another curve ball sent by the Small Suzuki Gods to melt your head.

Definitely. I didn't think there's any correlation between the two. Just thought it was quite the coincidence. At least I have the kick as a backup!

I ordered two brush kits a while ago for my 850 starter that I haven't used yet. I'll have to compare PNs to see if the 750 uses the same. If so, I'm in luck. If not, I'll probably be kicking for a while...

 

[93Bandit]

Petcock Rebuild update: I've put 100 miles on the bike since the petcock rebuild, and the bike has been heat cycled a handful of times during that mileage. So far no signs of leakage, bike is running pretty well. Maybe the rebuild was a success?

Also, would anyone like to comment on my final carb synch gauge readings? Are they close enough?

 

[93Bandit]

Well folks, sad day over here. I sold the 750. I got to the point where I couldn't invest into it what it really needed, in a reasonable amount of time. I set out to revive it, get back on the road, and I accomplished that. Yes, it still needs a lot more work but I proved it is worthy of a restoration. A gentleman from Ohio picked it up today, along with the 750 parts bike I had. He seemed like a good guy, I think it went to a good home. He didn't exactly state his plans, but it sounded like he wants to restore it. I mentioned GSR to him, he wasn't aware of the site. I'll send him a link so maybe he can join and continue what I started.

I'm down to only one bike in the stable, but during this chapter of like that's all I need. Having less projects will allow me to dedicate time and funds towards the many put off maintenance items on my 850L.