Arrow Enfield Airfield? Gearbox problem

[alanbrown]

Having built up my 250 engine, originally planned for fitting into a Bantam frame, I was concerned about the brakes and suspension on the Bantam, having had a few, and decided instead to fit the engine into my Royal Enfield Bullet. This has a 7 inch TLS brake and well sorted suspension front and rear. The conversion was fairly straightforward but required a down tube adding to the frame, and engine mounting plates to pick up the footrest mountings on the crankcase.A 6mm spacer was required with the new 55tooth rear sprocket

I used exhausts off a Yamaha TDR250, with quite a few mods to fit. Exhaust silencers are Honda NSR 250

It goes well, first time out today, and the gearing is just right. It handles well and stops well too, probably because the Arrow engine is 25kg lighter than the 500 bullet engine.However during the course of the ride I gradually lost 4th gear, and now selecting 4th is like a neutral.

I will have to strip the box down, but before I start are there any suggestions regarding the reason for this, is it selectors, or maybe gears moving on the main shaft? I did replace a bush in the back of the case. Any help appreciated.

Alan

[AndyEames]

Hi Alan. Could be a combination of worn dogs on the sliding gear that engages with the sleeve gear and/or worn pins in the selector shaft where it runs in the selector drum. We make ours out of silver steel butvI think you can get them from Drags.The iron bushes are prone to wear. Has the flange on the bush disintegrated ?
Andy

[john W]

Hi Alan is this the same bike that was on the facebook Arrow and Leader site that had a Siamese exhaust pipe fitted please? Looks the same bike
to me but under a different name. I have a 250 gt Continental with a Leader engine

[alanbrown]

Yes, well spotted, it's the same bike. I started off with a siamesed system,using 2 arrow front pipes, and the 4 stroke exhaust from the Bullet. I also have a Yamaha TDR 250(what a bike!) and this came to me with a spare exhaust system. I wanted an expansion chamber and decided to use the TDR pipes. These use a crossover layout to get the correct tuned length. I wanted to retain this and this meant a lot of modifications to fit the system to the Arrow and fit around the Downtube frame member that I had added.
But all worth it, the bike has a power band and revs out well which the original system never did.
Not noisy either,the Honda NSR250 cans work well. I would prefer the outlets to point down rather than up, but that's a detail I can live with.

Do you have a photo of your GT Continental?

Cheers
Alan

[alanbrown]

[john W]

The picture is on facebook and sadly I don't know how to load it up on here see attachment if it has worked

[Eero.Korhonen]

Is that legal in U.K. to change engine? Certainly not in Finland, but most of these young policemen don't understand
old motorcycles.
Br, Eero

[grahamhibbs]

Yes it is but it but the EU are trying to make it much more difficult as they have done in Germany, the best and most well known example is the Triton.

[Eero.Korhonen]

But you not in EU anymore, am I right?
Br, Eero

[grahamhibbs]

Yes unfortunately for another year we are.