BIMOTA GT1 Project

[wolfgangh]

I have some new pictures to share. Today I married the frame and the engine - it is so easy with this frame, you just lift the engine into place from below.













Here it is in good company with some of my other bikes

[RING_DING]

Coming along nicely Wolfgang! Your attention to detail is superb

[Suzukidave]

Very nice You arnt going to be able to ride it anywhere without drawing a crowd Whats going on inside the engine that you can share ?

[rngdng]

Very nice You arnt going to be able to ride it anywhere without drawing a crowd Whats going on inside the engine that you can share ?

I see a lift plate......




Lane

[Suzukidave]

Good eye Lane maybe 3mm ?

[wolfgangh]

There is not so much done inside the engine - I bought the engine as is. 3mm cylinder spacer, TR750-like porting (previous owner opted for 32mm exhaust from TDC - I hope this is not too radical!), cylinderhead shaved off 1,5mm, BARTON close-ratio gears, VM32 carbs, ACCENT ignition, JEMCO pipes.

Since I am not looking for a race bike and the engine tuning seems to be on the radical side, I am planning to change barrels and head over winter to a more conservative version. I want torque. I will try it as is first.

[Suzukidave]

I am pretty sure what ever spacer you add under the cylinder you have to remove a like amount from the top just to keep compression the same , for a torque engine stick on some reeds

[wolfgangh]

Of course the barrels have been shaved off by 3mm. Correction on the carbs, they are VM34.

[Suzukidave]

Of course the barrels have been shaved off by 3mm. Correction on the carbs, they are VM34.

Sorry , should have known better than to suggest

[rngdng]

That engine set-up is a lot like mine. It still has a good bit or torque.



Lane

[wolfgangh]

Made good progress this week.
Completed engine assembly, installed Accent ignition, and mounted VM43 carbs and JEMCO Pipes.







Fitted an external gas tank and started engine time. This thing is so F....g loud, I dont think any real TR750 was ever louder. Besides gettign air filter pods mounted, there is not much more left to reduce noise. I seriously cannot imagine how anyone can ride his kettle on a public road with JEMCO´s - I dont think a stock airbox makes such big difference. Don´t get me wrong -I love this sound, but it makes it impossible to use this bike in my country. I hope I find ways to reduce noise level significantly. Any ideas welcome.

Here is a short video - turn volume to max to get an idea of what I am talking about

https://youtu.be/qkUVLFUDM4o

[tz375]

I think that the muffler volume is too small and the steel shell resonates.

As a quick fix, see if you can find aluminium tube that slips over the existing muffler shell. It 's a tight enough fit (no rattles) it will reduce noise radiated out from the side of the can.

If that doesn't work or work well enough, try to cut the outer muffler shell off and fit an adapter and larger bore aluminum outer sleeve and more sound absorbing mat around the stock core.

You might also try a smaller core perforated tube, but too much smaller and it will overheat.

If that is still not enough, you may need to design a different baffle arrangement, but try larger volume and softer outer skin (Al) first.

[fredvincent]

This raises a question I was going to ask as part of my upcoming GT500 race rep build - Gordon Jennings advocated in his book that trials with extending the tailpipe into the baffle cone reduced noise and in some cases increased power slightly. Does anyone have any evidence that this has been tried since he wrote the book back in the 70's?

[Suzukidave]

On my last custom GT i used this idea when building the chambers , i inserted the stinger into the last cone . The exhausts are still quite loud but i cannot tell how loud they would have been in normal fashion .

[smokin_blue]

I ran internal stingers on the pipes on my GT250/T330 build shown in my avatar.