Frankenstein

[old smokey]

Here is the new starting point.
This is what a beat down GTR looks like with a Yamaha 500 front end.
Still plenty of work to do. But in my own twisted way, I like this beginning.
At least it can track straight again.

[old smokey]

This is the lower race cup swapped from the Yamaha 500 that fits perfectly in the GTR head tube.
It reads "THSO605V" and was made by Koyo.

[Bikenstein]

Much better Smoky. Have you decided on a paint color? For me I would go red, use the GTR headlight and drop the turn signals. But that's your baby so do it like you want it. Should be a big improvement with the front brake.

[old smokey]

I haven't done much planning with colors yet. I'm thinking maybe two on the tank, but not sure.
Turn signals aren't pretty, but I think I'm going to add them for safety.
Possibly going to remove Yamaha gauge cluster and modify mounts to use original BS ones.
The headlight bucket options are being considered, but mine was damaged by the deer so it costs money either way.

[reed]

Dave,
Looks like the Yamaha fork will work on your Bridgestone!!
Good luck.
Steve.

[old smokey]

Steve, it was a pretty simple swap. It will require some modification though to adjust the steering stop limits. Although my trial fit with the Yamaha tank in place is having it fully forward - maybe I can slide it back and prevent the tank from being the first thing the forks would hit.

[old smokey]

Plans will be to have some custom expansion chambers professionally made, but I need to get the engine repairs completed and back in the frame to do that. Has anyone that has made or used expansion chambers had the stinger extend half way back into the main chamber? I read the old article by Gordon Jennings and he talks about that as a great way to reduce the noise of the chambers and have no noticeable decrease on power. I don't remember if I found the article on here or somewhere else on the internet. It's called "Do you really want to know about expansion chambers?"

[old smokey]

Pulled the bike out in the sun yesterday and took pictures with various combinations.

[old smokey]

Stock parts on bike from left side view.
I forgot to put the stock headlight bucket on for these 2 shots.

[old smokey]

Here is a little more of the direction I'm thinking of going. Not sure how, but I think I will be modifying the seat pan. Maybe build in the brake light and license plate.

[BRT-GTR]

Smokey,
 I read something on expansion chamber stingers only the other day. Normally I can't remember what I had for breakfast but have a look at Page 6 of 8 in 'Son of Secret Weapon, Part 3' in the '350 Road Racing mods' section of Manuals/Articles on this site. Having used tuned pipes on model aircraft engines, the suggestion of pushing the stinger in, up to the fattest part of the chamber seems to make sense. As far as I know the length of the stinger does not affect power, the exhaust gas has already expanded before it goes into the stinger.
 The reverse cone on the expansion chamber is hit by a sonic wave from the exhaust port and bounces it back to stuff the fresh charge back into the cylinder, thats my basic understanding. So if the stinger is welded directly into the back of the reverse cone, its allowing the some of that sonic wave to escape to the exhaust with the consequent noise. Moving it forward should reduce the noise. I'm no expert but it seems logical, give it a try and let us know. Something certainly made Son of SW unusually quiet when you read the article.
On the other hand , if its that simple why did we have so many noisy 2 strokes on the road in the 60s and 70s ( me included) or am I just getting old.
 Hope this helps,  Brian

[old smokey]

Brian, thanks for the thoughts on that. When I get caught up to the point of being ready for chambers, I think I'll ask the fabricator to have the stinger extend back into the middle of the largest diameter unless he has a strong argument against it. I hope that happens this summer, but time is going quickly.

[slawsonb]

who are you planning to use to fabricate? and are you going to follow the recipe in the Tuning for Performance section of the manual?
I have plans to pursue this, but further down the road...thanks
...bert

[old smokey]

I don't really plan to follow the tune-up guide. No cutting of the intake valves from stock, or modifying the heads or gaskets. My main thoughts for expansion chambers would be to have a different look and if it gives a little performance improvement - bonus. Having the cylinders plated back to stock condition should be an improvement as they looked like there was scoring/damage that was there before I owned it (33 year ago). The cylinder plating cost $550 so I don't really feel like gambling with port cutting either. I am hesitant to mention the manufacturer of chambers because if I use him I would own his design for any future GTR sales he might do. Do I think he could sell more chambers for GTRs - not likely.

[old smokey]

I talked with the local professional expansion chamber maker as I'm expecting to move out of the area soon. He couldn't accommodate my short notice, but we talked for a bit.
He said he does not recommend having the stingers extend back inside the main chamber area. He said his experience is it does make them quieter, but it does cause some power loss and makes the power band even more peaky. He said it can also cause problems with heat being retained which can lead to piston problems.
Once I am relocated and hopefully make progress on the rebuild I can send him brake lines bent to the routing I want with various clearance diameters noted along the length of the brake lines and he can make chambers without ever seeing the bike.
Someday....