bike engine conversions

If you're changing the engine in your Midas for something different we want to read about it. Every possible conversion and more can be found in here...

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bike engine conversions

Postby rocketron » Sat Feb 28, 2009 10:24 pm

I know that bike engines are powerful, lightweight, cheap (from bike breakers) and all sorts of minis are fitted with them, either front or rear mounted, but I have a nagging worry that they may not be as reliable as we might suspect.
At a 2 day race meeting at Anglesey last year, there were four very lightweight, spaceframed, rear-engined and grp bodied minis competing in the same race. Three had various bike engines and one a supercharged honda 2litre vtec, about 300+bhp! These were super bits of kit and was very impressed by them. On each day, these cars had one "practice" session of about 15mins. and two races of 20mins. The vtec had problems initially but when sorted went like hell, for a bit, until the engine did itself in. The bike engined ones also went well, but did not complete the second day's racing.
In conversations with other petrolheads, the consensus was that we all expected the bike engines to have lasted better since two of their drivers said their engines were or very near standard tune, all the minis were much lighter in weight than standard, the lightest being less than 700kgs. Even if all the bike engines came from a scrappy, can it be sheer coincidence they all failed? Does hauling 700kgs of mini instead of a bike make a difference?
I'm not sure what their lap times were, but am certain were not as good Metro Challenge or Mini Milia.
One-time Midas owner, Pete Hills regularly sprints (OK, I know it's not racing but bear with me) his very lightweight and quite superb mini and to my knowledge has only suffered one engine failure. Pete does not pussyfoot about when competing and often gets good results. He does all his own work and I respect his skills very much. So I would say his 1275 A series engine is very reliable? Also, in other mini race series, often with more than 20 cars per race, I never expect to see more than one or two cars to retire.
So the question I ask is: In general, can I expect a bike engine, tuned or standard, when front wheel drive fitted to a standard weighted mini, or Midas, to be as reliable as a decently built 1340/1380, when subjected to everyday use and the odd thrash?

There was also at a sprint a lightweight mini with a BMW k1000 head conversion on an A series; Cost about £8k so far. The conversion was interestingly different but I thought expensive: perhaps a honda vtec, ecu change with cams, up to to 250bhp?......now we're talking bangs per buck.I don't think the 1380 that left him for dead cost that much!

Any thoughts?

Ron.
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Re: bike engine conversions

Postby ACDodd » Thu May 28, 2009 10:38 pm

I think you'll find that a properly engineered bike engine conversion would go very well. But using second hand engines verses a properly build A-seires is not a good comparison. Comparing the 2, an A-series that produces its torque much lower in the rev range is much less stressed than a high revving big bore short stroke bike engine. If you take a healthy sprint A-series it will have about 110lbft of torque or more. If you look at a bike engine you will be looking at about 80lbft of torque per 1000cc/typical bike installation. So even using a 4.6fd over a 3.93 fd the torque that is delivered to the wheels is more in the A-series installation. Coupled with lower rpm means a service life. Bike engines lack torque. What you do is lower the gear ratio to magnify the torque delivered to the wheels. This makes the engine rev harder meaning more stress. If you want a fast mini you need a 2 litre or 2.3 litre engine with a Multivalve head. Using a 2.3 litre bottom end and fast road cams on any typical large valved 4 valve per cylinder engine will get a solid road driveable 225bhp all day long. Put this with a FD of around 3.6 and you will have a beast with twice the torque at the wheels. And much much faster and you won't have to rebuild it.
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Re: bike engine conversions

Postby rocketron » Sun May 31, 2009 11:06 pm

Thanks for the reply. I agree with you about torques from well built A-series and lower revs and different final drives to suit diferent torques etc. the minis at that race meeting at Anglesey were all cars from "Z-cars", one of which was and driven by the company owner. I would have thought that his would have had a "properly sorted bike engine conversion"?

Fit a good big 'un instead!
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Re: bike engine conversions

Postby bjw970s » Thu Nov 12, 2009 12:46 pm

Hi Again Ron!

As you will gather from my other thread I also run a Fireblade 929 bike engine'd STM LOCOST. The car weighs 450Kg and has a engine from a scrappy which I have run 2 race seasons with and was in when I bought the car. It has uprated cltuch springs, a power commander, baffled shortened sump and thats all.

The car has taken some getting used to (ie lack of torque etc) but the engine has been very reliable 'out of the box'. The beauty of Bike engines is:

They are tuned for performance even as standard.
They have sequential dog boxes as standard
They are £300 - £500 from the scrap yard for the lot.
They weigh around 65 Kg.

Now if you consider that my 'nearly' (full spec miglia engines only last 3 races - no thanks!!!) miglia spec A-series engine probably cost £4K to build and I was very careful in sourcing parts (dog box costs alone were scary.....) and probabaly kicks out 125 bhp and my fireblade engine cost £450 and kicks out 140 bhp, and comes with a sequential 6 speed box then the benefits are there.

The issue is weight. I was fortunate that a friend of mine has built his own kit car model called the 'fletcher hornet' and has built a Bike engined variant. He has taken into consideration the factors and advised my how to drive the bike engined car (BEC); when to down shift more use of brakes as opposed to engine breaking, car balance benefits through the corners etc. Ironically as I run a 970s it was less of a surprise to rev my BEC to 11,500 for gear changes as it could have been; you need to learn in a BEC to be careful with the clutch which can be done and still achieve results.

As I have 2 engines that I had built up over the years I will be using A-Series in my Midas intially. But, With the benefits of a BEC or even a VTEC, I may change later (considering mid engined BEC configuaration) for cost alone (sadly) as, supporting a competition A-series habit is painful!

On of the factors will be whether I can safely make the front end removable..........

Brian
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Midas MkII Project
Mini Cooper 970s
Mini Clubman Estate
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Re: bike engine conversions

Postby manifold » Thu Nov 12, 2009 4:26 pm

i would love to see a bike engined conversion in any midas. the FWD promotive one looks good to me. ;) Easy conversion too. RWD z-cars type ones are achievable too....in a different frame.
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Re: bike engine conversions

Postby rocketron » Thu Nov 12, 2009 7:35 pm

Well hello, again! Right, let me state that I have absolutely nothing against bike engined cars in any motorsport discipline, and I don't agree with the MSA non-acceptance of bike engined rally cars. I'm all in favour of "alternative quality engineering solutions". (see Andy Burton's Peugeot Cosworth on YouTube, if that doesn't raise your spirit, then you must be dead!)

My original concern was that on the evidence of, now, two race meetings, maybe there was a reliability problem with dragging heavier weight than a bike, particularly a race, say, than with hillclimb or sprints, where cars run for possibly 4mins max instead of 15mins as in a race.

What you say in the second half of your last post, re driving manner, makes sense. Perhaps this may have been one reason for those engine failures we saw: smoothness of driving probably disappears when battling for a corner!

Front ends can be removable on Mk1/2. Have done it, fitted struts from front end of subframe back to bulkhead. The engine was NOT very powerful, would imagine a torquey lump may cause problems- I don't know.

Now, a bike engined Midas looks like another "hilarious" option. Youv'e got to do it! How can you not!

Regards, Ron.
p.s. My Dad wouldn't like it!
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Re: bike engine conversions

Postby bjw970s » Fri Nov 13, 2009 8:41 pm

Hi, Ron - totally agree with you on all points - just offering my limited experience thus far to add to the debate.

I have raced with RGB 750mc cars and spoken at length to a chap called Ian Gray who runs Stewart Taylor Motorsport. As discussed previousy the advice I have received is that there are 2 factors; weight and driving style. Some people racing have no mechanical sympathy and have a poor reliability record engine wise. Driving BEC's is however an aquired taste which is about momentum over torque etc. I have friends who run; Suzuki V-twins, kwasaki 1100's and blade engined cars and driven via chain and propshaft; engine has not been the issue in the reliability stakes. So with a light'ish car, I am quite impressed so far and have had good tussles with 200 bhp 205 gti's etc. When battling for a corner you can carry much more speed through and down shift very quickly use different braking points etc - As it was explained to me by a race instructor its all about using the car's strengths. Just as a point of reference we take part in a 6 hour race on the Silverstone International circuit and I have run my BEC in that race for 55 minutes non stop.

My mate is a bit of an engineering guru in a quiet way. He has had his 'fletcher hornet' featured in car and car conversions in the past which he self built from scratch and made a small run of kit cars to qualify for the 750 kit car series, with crossflow, V8 and BEC variants. It was his experience that prompted me to go BEC. He is interested in doing a MID ENGINED/ Rear engined (can never work out the difference) and was intrigued by my MIDAS and the possibilities of doing a conversion on it - problem? he is too busy at the moment to take it on and I wouldn't dare attempt it on my on without his engineering expertise. (couldn't waste a good MIDAS). So I will park that one for the moment!!!

So positive on BEC's as a concept for power to weight and cost but think there are weight limitations (vehicle wise) and driving considerations for use. Also, as Ron has said, A BEC would not be allowed in rallying so, will the car be race only from the outset.........

Brian
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Midas MkII Project
Mini Cooper 970s
Mini Clubman Estate
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Re: bike engine conversions

Postby Stuart » Mon Oct 18, 2010 8:01 pm

manifold wrote:i would love to see a bike engined conversion in any midas. the FWD promotive one looks good to me. ;) Easy conversion too. RWD z-cars type ones are achievable too....in a different frame.


I'm not sure I could put up with the noise, then again I can't even stand the noise of a standard Midas A-series these days


Looks a bit on the low side

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Re: bike engine conversions

Postby d.woodspeed » Wed Nov 03, 2010 12:45 pm

Has anyone actually done a bike conversion on a Midas? This is an option which interests me, but it seems like a bit of an engineering nightmare, if you don't know what you're doing!

In my case, a decent A-series would probably be an easier and safer route, but I'm open to advice/encouragement!!

Cheers,
Dave.
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