82 GS1100E Mr Turbo Rebuild

[oldGSfan]

I'm far from an expert but sharing what I read up on. The original carb with the Mr Turbo or American Turbo Pak (it's confusing) kits was a late 70's HD Keihin 38mm which seems to be universally hated by HD folks, FWIW. The guy that raced mine used a S&S Super B for Bonneville, and I read they are good for all out open throttle but not so street friendly. All signs pointed me to the Mikuni HSR (42 in my case) so I got one since both the Keihin and S&S needed rebuilding and didn't look so good overall with stuck butterfly and hacked up or missing choke, etc. Right now may be too early to judge but it's idling fine and starts right up with a couple twists for the accelerator pump and a bit of choke when cold.

I think the Rajay is a robust turbo but now there are better choices. Plus there is the draw through vs. blow through choice. Gaskets and rebuilding are scarce and expensive. I read that it is slow to spool and will come on with a major bang. Will see. I am too old to go nuts on a turbo bike, it's just a cool thing to have and restore, ride here and there.

I am fascinated with building a turbo setup like the Mr. Turbo kits. I can select a turbo and build all of the parts. The part I know nothing about is the carburetor. What carburetor does this kit use, and does it work well for a street ridden bike that doesn't get whooped on a lot?

 

[chris]

That seat is a good score. Mine split in the same spot.Two things I never do are body paint and upholstery except dirt bikes that's because everyone will know I did it myself. So I vote professional upholster.

 

[Rob S.]

So I vote professional upholster.

I concur. Mine was reupholstered, I'm sure, but looks exactly like all the pics I've ever seen from 1982.

 

[oldGSfan]

Edit/update: Took to a local upholsterer and he said the material is too thin, it will tear again etc. Pretty ornery sort of dude, I appreciated his honesty but he just kept saying the same stuff over and over, and I heard him the first time.

Yeah I will have it done, it's too good to leave to a hack like me. I got it today, it's really good other than that split, like new, made my day opening that box.

That seat is a good score. Mine split in the same spot.Two things I never do are body paint and upholstery except dirt bikes that's because everyone will know I did it myself. So I vote professional upholster.

 

[Guest]

I'm far from an expert but sharing what I read up on.

Thank you. What have you learned to be the maximum power that can be squeezed from that carb? I would like to build a turbo GS one day, and think around 120-130HP would be more than enough. I'm not trying to threadjack.

 

[oldGSfan]

Read the posts by Rajay on this link, they are very informative on the HSR and draw-through overall. The numbers are more than double what you are after so the HSR42 is fine. There is a wide variety of main jets. Also this YouTube video of a '74 Z1 with the same setup putting out 120HP is a good watch.

Thank you. What have you learned to be the maximum power that can be squeezed from that carb? I would like to build a turbo GS one day, and think around 120-130HP would be more than enough. I'm not trying to threadjack.

 

[Guest]

Read the posts by Rajay on this link, they are very informative on the HSR and draw-through overall. The numbers are more than double what you are after so the HSR42 is fine. There is a wide variety of main jets. Also this YouTube video of a '74 Z1 with the same setup putting out 120HP is a good watch.

Thank you very much. I have started a new thread so as not to clutter yours needlessly.

 

[oldGSfan]

Bike done. 183 HP on the dyno, not sure the boost he was using yet. I told him to go easy . Going to pick it up today, am so amped up to ride it - I better settle down....

 

[bull958]

Turn it up, don't be a pussy. 183 is hardly enough to get into trouble with. LOL

 

[steve murdoch]

Bike done. 183 HP on the dyno, not sure the boost he was using yet. I told him to go easy . Going to pick it up today, am so amped up to ride it - I better settle down....

A hundred or so extra hp from stock? Fantastic!

 

[oldGSfan]

Yeah at least, this is at the wheel not crank, guy said probably has 80 HP at wheel stock. He said it was extremely well built and has hot cams so it idles lumpy at about 1500 RPM (13.5 air-fuel ratio), and he had it up to 11K on a couple runs as there's no rev limiter. There are no charging issues, it was due to not having resistor on plug. 80MPH in 3rd gear is monster wheelie time. I have a couple things to fix, the front springs should be replaced but I may try a spacer just to see how it works. The petcock leaks at the bolts, but I have new sealing washers. The centerstand is coming off, it rubs the chain as there's no stop, and it's too short anyway. Little stuff I can do in a day or two before riding. Here is one of the runs.

A hundred or so extra hp from stock? Fantastic!

 

[dorkburger]

So cool. .

 

[steve murdoch]

It will be interesting to know what level the boost was for the recorded runs.
A couple weeks from now when you are bored with the 183 hp you will need to know how much to turn it up. haha.

 

[93Bandit]

Awesome! It's nice to finally hear some numbers. I'm curious how well mannered it is on the street?

 

[Guest]

I'm curious how well mannered it is on the street?

So am I! I would also love to know what the jetting is on the carb.

 

[oldGSfan]

18 lbs boost. I've only ridden it a few hundred yards, so I can't judge by that. I will see how much I can get done today, the too big tire from front will be fine for rear of my '73 CB750 and the smaller front should be right for handling.

 

[Rob S.]

I need to see/hear audio/video. I NEED it!

 

[oldGSfan]

My son has a GoPro type camera (a Rylo FWIW) and a chest mount, I will try that. Honestly I'm going to be old and slow on this thing. Even though I ride a 150HP Multistrada, and have owned and ridden several 750 and up bikes - probably north of 100K miles all over the world - I am cautious by nature and know that my reactions and vision aren't what they used to be. Have to be honest with myself. I've never been a fast rider, just a competent and careful one. So why a beast of a turbo? Because it's cool and I like it, even if I never redline it that's OK by me - better a live pussy than a dead duck

I need to see/hear audio/video. I NEED it!

 

[Guest]

18 lbs boost.

That's much more than I was expecting. Are the pistons and/or rods non-stock? How is retarding of ignition managed?

 

[oldGSfan]

Pistons are supposedly 6.5:1 and sleeved down, according to previous owner but I don't know the details beyond that. He was a rider not a builder, but all the stuff he told me checks out, not a BSer. I have a receipt from Don Vesco that says 'fit studs, ''valve job & port, 'cams timing drill cam to fit gear & tap', 'weld crank' and 'fit turbo'. Cam timing 25 btdc I think. A bit lumpy.

There's an Arias piston brochure in the stack of paperwork that goes down to 7.8:1, and that's 74mm not undersize, so it's a mystery until such time it gets opened up. The bad news is that there is a very slight leak in the top end (need to trace it with dye) that may force that, will see. I'm hoping it's the normal tach drive, I just got a new seal. Maybe it's a copper head gasket as those were/are used for race engines, and I understand they shrink with heat cycles.

The tuner sees a lot of bikes and he was crazy about it, saying it's really tight and strong. He's ridden it more than me at this point. He is brother-in-law of Wes Cooley Jr., and he spoke to his sister about it and she said that Wes's father was pals with Vesco and would s*&t himself to see the bike. I think the tuner is mixed up thinking it was Vesco's bike, it wasn't, his shop just did the work and it must have been a tight LSR community back then (as now I'm sure). Anyway it's a cool circle, he knew all the old-timers like Pops Y, Kerkers etc.

@Longitudinal - jet size 240, biggest they make for the HSR42.

That's much more than I was expecting. Are the pistons and/or rods non-stock? How is retarding of ignition managed?