Hitchcocks Forum

I often use my 350 Bullet to explore un-surfaced roads and tracks; some of these are quite steep and there have been occasions where the bike has run out of revs in 1st gear. I'm considering using the bike for "Classic" trials, which involve a road run of up to 200 miles, interspersed with off-road hill sections. These sections are deliberately chosen to be "challenging".

Obviously, lowering the gearing is what's needed. I've obtained a 15T front drive sprocket as one step in that direction and this will get fitted in good time.

However, I've also been looking at buying a "trials" gear set from Mr. H. I see the big disadvantage of fitting those is for road use it leaves a large gap between 3rd and 4th gears.

Another alternative is to fit a right hand gearchange, 5 speed box from a Bullet 65. These seem very rare to find and I simply can't justify the price of a new one - certainly the one advertised in the Bullet catalogue is almost as much as I paid for the bike.

Has anyone personal experience of riding a bike with the "trials" gear set fitted? Any info gratefully received.

I completed the Beamish on a 350 years ago and all I did was fit a smaller gearbox sprocket. Can't remember what size.

Peter,

Thanks. A quick calculation, using the ratios given in the H's Bullet catalogue tells me that fitting a 14T front sprocket would drop the ratio of first gear to about the same figure that the pair of "trails" gears would, obviously without the advantage of keeping the original 1:1 top gear.

I'll probably fit the 15T sprocket I've already bought as an initial compromise and see how I get on with that.

I'm looking at doing something similar. The way I worked it out (and my maths is often suspect) is that dropping it to 15t will reduce top speed by 6.6% and dropping to 14t will reduce top speed by 14.3%.

So if it does 65mph flat out on 16t, it should do 61mph on 15t and 56mph on 14t. With the caveat that it's more likely to be able to achieve that theoretical top speed.

I decided that in the context of a trial, I could live with a top speed of 56mph.

Of course the third option is looking at the REAR sprocket. Our hosts do a machined rear drum with a selection of bolt-on sprockets. This would leave the option of reasonably simply changing the gearing without having to dismantle half the bike. Also means you are using larger cogs, which in engineering terms, is generally better than using smaller ones when considering tooth loading.

Hi, 350 Madras enfields are overgeared, Redditch models had a top gear at 5.67 which is equivalent to a 15t gearbox sprocket. So unless you want to change internal ratios a 14t sprocket will be a good compromise. Vince

Changing the rear sprocket for a larger one also involves buying the machined brake drum and a new, longer chain.

A quick look in the Bullet catalogue tells me that the total cost = £175 plus postage etc.

That's over 10% of what I bought the entire bike for.

I bought my new 15T front sprocket for £12.99 delivered and the standard chain can be used with it (an' I've recently fitted a brand new one).

My bike is mildly tuned and runs very well once it's "on song" on the flat. I do use it on motorways when necessary and it easily keeps up with the HGVs doing 60 and I sometimes overtake if I'm feeling very brave, but it often runs out of puff in top on a steeper uphill stretch. When have to change down into 3rd it reveals just how big that gap in the two upper ratios is. Dropping the front sprocket size (rather than the "trails" gears mod to the gearbox) has a side benefit of reducing the gaps between all the intermediate gear ratios, too.

So I think I'm probably just going to stick with Vince's advice, a low-cost compromise is often a good thing.

Now, all I need is to find out which extractors/special tools I need to get the sprocket changed.

"has a side benefit of reducing the gaps between all the intermediate gear ratios, too"
No, the spacing will be the same, just lower.
If you want to reduce the gap between 3rd and top then Mr H's "close ratio" conversion is the answer. This raises the gearing of 1st, 2nd and 3rd. Given that you want to lower the gearing this may not be the answer though.

Peter, the difference in the overall gear ratios, which is what we're talking about, will be reduced by a factor of 1/16th.