Evening all,

Finally got my first drive of the CBR1000F powered Locost on Sunday (brief trip to Aldi and back).

The acceleration is phenomenal compared to what I’m used to driving - and even started to get used to the massive clunks/crashes up and down through the gears towards the end.

On the way back however, I took the short hop down the dual carriageway. I was told when buying it that it was 5 speed - which was very suspect as all research suggested that it only ever came with a 6 speed box. Very quickly I ran out of gears and didn't seem to be going very fast compared to the screaming from the exhaust and the vibration through the chassis.

After checking the spare engine I recently bought – which had 6 gears marked on the casing, I got underneath and checked again. It looks like some previous owning so-and-so has ground off the 6 from the outer casing presumably due to losing 6th at some point and not wanting to strip it down and fix! So until I replace the motor in the winter I’m stuck with 5 gears

My calcs and the gear calculator sheet in this area have basically come out the same – at 60mph which is nothing - I’m turning approx. 7300rpm which seemed about right from memory of Sundays run. Bearing in mind 60 is a fairly common sensible speed for a car, I’m looking for ways of making it more ‘liveable’ with.

The silencer is not in the best of nick and had the DB killer removed so that wouldn’t have helped. So I’ve today ordered a long repackable Wunoff jobbie that they are running an offer on which should help.

Is there anything else I can do in the mean time to make it a bit more liveable with? I’ve looked at a lower diff ratio (3.5) which might be an option for the winter rebuild. Does anyone have any experience with this – does it help a lot?

Cheers
Tony

Not really many other options other than bigger diameter rear tyres?

3.54 will help significantly.

I suspect that what you really want is https://www.retroford.co.uk/product/3-31-english-crown-wheel-and-pinion-cwp-3-3/

And a 6th gear obviously.

Not the same engine gearbox but my zx9r powered striker was running a 3.64 Sierra diff and 185/60/14 tyres in sixth gear mph per 1000 revs was 10.3 mph it topped out at 12000 revs which was 124mph if I could of changed it to a 3.1 approx diff it would make it a lot better on motorway runs it was fun and very rapid

Thanks for the replies all - I realise that BEC's are far from relaxing at higher speeds when compared to a CEC - but it just seemed far too much - and now makes a bit more sense.

I did briefly think about larger wheels - but the circumference of a 195/50/15" is exactly the same as the 205/60/13's I have on now so wouldn't gain anything. I personally think 7's look out of proportion with anything larger than 15's anyway (no offence intended to anyone who has btw).

The gear ratio calculator on here has the exact engine in the drop down list and shows it topping out at 100mph flat even if I had a 6th - so I think further work definitely required here. Thanks for the link to 3:3 diff ratio too. I guess this is about as low as they go without losing too much acceleration?

It certainly explains why I was taken on the route I was on the test drive. Redditch has a big ring road which is fast in a lot of places so I was surprised when we didn't go near it. Again, makes sense now..... Oh well, better start saving some penny's!

Cheers again
Tony

There's a possibility that you either have a CB1000F engine or gearbox, which would be a 5
speed, I believe that they were all but identical otherwise.

I wouldn't wait till winter though, it shouldn't take more than a day on your own to swap an engine, you cant drive not at the =moment anyway.
Better than hating it till then

[Edited on 7/4/20 by ReMan]

quote:

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Originally posted by ReMan
There's a possibility that you either have a CB1000F engine or gearbox, which would be a 5
speed, I believe that they were all but identical otherwise.

I wouldn't wait till winter though, it shouldn't take more than a day on your own to swap an engine, you cant drive not at the =moment anyway.
Better than hating it till then

[Edited on 7/4/20 by ReMan]

---

Why not just split the spare and swap the gearbox then?

quote:

---

Originally posted by ReMan
Why not just split the spare and swap the gearbox then?

---

You got me thinking more seriously about the engine swap ReMan! So I just went out and did a proper check/measure up etc to see what it would take.

It actually looks like the carbs/rubbers that I've got on now will fit the earlier model! The ports on the head of both are angled (V shaped slightly) when looking from above - it just seems that the rubbers on the later models take out the angle so the later carbs can sit straight

Apart from the head water outlet hoses connection points being in a slightly different position (which a new length of silicon hose would sort) - everything else "seems" to be a straight swap

Gotta be worth a punt to swap it out and try it I reckon even if it is a couple of weekends work - so will give it a go.

Thanks again everyone

Just a slight update,

I've got the existing SC24 engine with the missing 6th gear out and on the floor (was an interesting fight with the prop adaptor bolts) - and the older SC21 replacement engine next to it on the trolley:-








I've replaced the 7 tooth trigger wheel ignition and 2 coil pickup of the older SC21 engine with the later 9 tooth trigger wheel ignition and single coil pickup of the later SC24 engine that was in the car - so that it will work with the wiring and ECU fitted on the car already.

I've also got the smaller 19mm silicone hose for the outputs from the head into an adaptor to connect back into the exiting 25mm hose to the rad.

Just got an issue with a couple of the exhaust studs to sort out and it should be ready for dropping in hopefully.

Whilst I was waiting - I thought it best to check what diff I have fitted - and have to say it's got me totally stumped!

I was expecting to have to turn the propshaft nearly 4 times to see the rear wheel rotate once, this would be a standard 3.89 ratio as I understand it?

I am totally confused though as 1 full turn of the prop only moved the rear wheel just over half a turn??? I got my son to check whilst I was turning the rear wheel and he said the prop mark came round twice when I had only turned the wheel 1 1/7th turns?

I have had a couple of beers and might not be thinking straight - but summat doesn't line up here does it? I thought the other rear wheel might need stopping from turning to check properly - so chocked that and repeated - but got the same result?

Anyone with a clear head help me out here lol?

Cheers
Tony

If you're only turning one wheel it'll half the ratio. So for a 3.89:1, one turn of the wheel will only require 1.95 turns of the input.

Ahhh, ok that makes more sense then. So it looks like I do have a 'standard' escort diff then as 1 wheel rev was slightly less than 2 prop rotations?

Thanks for the help - much appreciated!👍

Does sound like that. To a more accurate result, turn the wheel 10 turns while counting input turns. Double input turns and divide by 10 to get your ratio. Be sure the other wheel can't turn.

Hi - Have you tried running the figures through the speed calculator at the top of the bec section.

Unfortunately the CBR1000F engine will always be at a disadvantage due to the high primary drive ratio. Even with a 3.11 diff fitted (which you don’t have the option of with a live axle car), mine would max out circa 105-110mph meaning cruising speeds were always quite high.

Cheers......

Hi Shandylegs - Thanks for the reply. It's nice to hear from someone who has had the same engine in a kit. What car was yours in?

Yes I've run the different options through the speed calculator so I realise it's never going to be a comfortable cruiser I just don't want my ears to be bleeding and my teeth vibrating out of the gums at 65-70 really.

TimC posted a link to a 3.3:1 gear set for the English diff which looks like as low as it goes for a live axle car. Popping that into the calculator gives approx 115 top speed at max revs.

That seems to suggest 80mph (which is probably the most this car would be taken to in all honesty) is approx 70% of the rev range. The CBR1000F revs to approx 10500 so 70% of that would be approx 7350rpm - which I could hopefully just about stand.

If I leave the current 3.89 diff in - top speed is approx 100mph according to the calculator. So 80% of the rev range would be 8400rpm which is probably a bit much for 'cruising'?

I'll continue with the engine change and get 6th gear back for now. Hopefully that along with the brand new Wunoff silencer will hopefully tame it enough for now.

I've got some 'interesting' findings from the engine that I took out - will post some pics at the weekend hopefully


Cheers again
Tony

Forgot to update this post with revised findings!

Removing the existing engine (with the suspected missing 6th gear) was fun. Someone had removed the sump plug and replaced it with a nut/bolt tightened up from inside so the oil was unable to be drained without undoing all the sump bolts and removing the entire sump. The sump had clearly previously had a wallop and had some grey filler stuff gunged onto it to stop it leaking - so I decided to just drill a hole in the sump to drain the oil and just replace the sump afterwards.

Once it was out, I could properly clean off the block and check the engine number. It turns out the bottom end is an SC30 prefixed number so is from a CB1000 (nicknamed Big one) after all - So ReMan was spot on with his guess about the 5 gears! The reason I discounted it at first is because it's def a CBR1000 top end.

So it looks like a previous owner has created a Hybrid motor by grafting a CBR1000 top end onto a CB1000 5 speed bottom end for some reason. I'm not too sure why either as I can't find any info on the net about the 5 speed CB gearbox being better/stronger etc than the CBR 6 speed?

So apologies to the seller on that point - he was correct that it was a 5 speed after all.

So, the older SC21 CBR1000 engine is now in the chassis and I'm beginning to connect up all the ancillaries. Looking through the inlet ports the exhaust valves look to have some oily residue on them so am not expecting great things as it seems the valve seals may well never have been changed - but I'll crack on and try to get it running to see.

Just going back to the main problem though - I don't think it's going to help my quest for non bleeding ears at 60mph though. According to my CBR1000 manual the gear ratios are :-

Primary - 1.786
1st - 2.75
2nd - 2.067
3rd - 1.647
4th - 1.368
5th - 1.174
6th - 1.045

Now I know it was a CB1000 bottom end - the info I can find on the net for those ratios are:-

Primary - 1.785 (almost identical to CBR)
1st - 2.833
2nd - 1.941
3rd - 1.5
4th - 1.217
5th - 1.040 (again almost identical to 6th on CBR).

So I think I'm right in saying that although I'll have the full compliment of 6 gears - I won't benefit as the ratio is the same (give or take)

I managed to win a 3.54 Crown wheel and pinion on Ebay last week and have had a reasonable quote from Kejja Motorsport who aren't too far from me to rebuild my current diff and swap the CWP out for the 3.54 at the same time - so it looks like that's my only option now to bring the revs down in any way.

Cheers
Tony