KR-1S.co.uk Forum

I have been looking into having a close ratio transmission made up and a full custom box is around £1300 - £1700 + VAT mark depending on how it's done.

To be perfectly honest, this was way over my budget and price range and was really after a solution at a third of the cost.

Having discussed this subject a couple of weeks ago with a fellow racer and forum member, we talked about the option of changing the 5th and 6th ratios only to keep the cost down.

Having looked at the standard ratios a little closer, I soon realised that this really would be a waste of time and money and more needed doing to get the benefit and really be able to call my solution a "close ratio box".

To demonstrate, here are the standard ratios, followed by the proposed ratio changes to 5th and 6th gears.

Standard
Ratio - % Drop

2.533
1.727 - 31.82%
1.316 - 23.82%
1.087 - 17.39%
0.963 - 11.41%
0.862 - 10.48%

Total % Drop 1st-6th - 65.97%

5th & 6th Modified
Ratio - % Drop

2.533
1.727 - 31.82%
1.316 - 23.82%
1.087 - 17.39%
1.000 - 8.00%
0.926 - 7.41%

Total % Drop 1st-6th - 63.45%

By investing a little more money and changing more ratios, I am proposing the following ratio changes;

Proposed Solution
Ratio - % Drop

2.333
1.727 - 25.97%
1.316 - 23.82%
1.130 - 14.09%
1.000 - 11.54%
0.926 - 7.41%

Total % Drop 1st-6th - 60.32%

I will be having this made over the next few months and there is a possibility of discount if I can get a few more people interested, so if you would like to know more and are seriously interested, please drop me an email to discuss further.

i think the 5th/6th was a trick the supercup boys used, top gear is like an overdrive in relatrion to 5th. having said that, in the era of supercup they were 150 quid!!! i1300-1700 is bloody expensive but if your planning to race for say, 5 full seasons its not all that much really. elf had his done for less than a monkey but i think he was bloody lucky and 2 was pally with the engineer who carried out the work.
i must say though, the 5th 6th alone work nice, after peak power in 5th, 6th is just right. 1 2 3 and 4 arent bad anyway on a bike with a rideable delivery, however if the 1st gear was useable at hairpins it would be spot on. t do this it would require altering the remaing ratios as im sure you have realised, hence the full gearbox decision. once you have gasped, how much?? you then remember a good few in f250/400 run dymags. price is ball park if buying new.

I've since been in touch with the engineering company the elf used and I'm going for a full 1R conversion quote and see what they can offer.

I think stan stephens used to do a kit that changed the top 3 gears, i know both the engines i run seem to have close ratio 4th 5th and 6th.

I found out by accident actually when i swapped engines for a spare one i had the big jumps between the top gears had gone and i didnt need a 14 tooth front sprocket.

No idea what the ratios are but im sure someone will remember from back in the day. I just bought an engine and it turned out to have flowed cases with shortened reed holders and that box in.

Might be worth asking the question though

Thanks John, I know all the ratios and Danny sent me a useful spreadsheet.

I am getting a full set made up, so will effectively be a 1R gearbox in my bike.

There was someone else interested in having one made up with mine, but I lost all my PM's and have forgotten which member it was, so please get back in touch with me, as I have started the process of getting this made now.

Ben

have a chat with Ellis at http://www.mpe07.co.uk/

I remember back in the day,1991 and i was struggling with lap times at Mallory Park. After chatting with the late Mick Lofthouse he suggested the 5th and 6th gear options. To cut it short, next time out i was nearly a second quicker and wasn't trying any harder. It worked for me.

I had a few KR's with the close 5/6 option. I spoke to Ellis at MPE about a high 1st to close the gap between 1 and 2 (which is too big) and a low 6th.
He can make up individual gears and they come in very reasonable. Also does full boxes at a good price.

I have gone for a high 1st as have found on the stock box that the 1 to 2 gap was much more of a problem than the 5 to 6. Will try that first and may fit a low 6 later - this is in my spare engine. Main engine has the 1R box in.

I've managed to find a supplier that will make a full close ratio transmission for around of £300 each, so myself, smithyrc and Bernie are going to invest in getting one or two each.

If there is anyone else interested, please drop me a PM by the end of this week, as he's finalising the price and I'm going to start the ball rolling with the order.

£300 for a full box, thats good!

...count me in

Tricia

Hi Ben,
I am on the road for the next few days, of you are free any time let me know and I will call in.
Cheers
Bernie

Yes I'm about all week.

Gearboxes worked out to be about £400 per unit including VAT in the end.

Rocket, Falconman, tzr Rider, smithyrc30 and myself are going for 1 or 2 each.

I'm collecting the money or deposit in advance and hope to place the order and deposit with the engineering company next week.

I have placed the order with the supplier today and he is going to finish off the drawings this weekend and then send them to production.

I am aiming for the middle to end of March for completion.

Phoned the supplier today to chase, but they are not yet complete. He's saying it should be done in another week or so from now guys.

Sorry for the delay with this, it's completely out of my hands at the moment.