Mad Idea OR Not

[haasad]

BMW K75 engine and box in an A7 special ? I'm drawn to this light, smooth, reliable, relative performance, three cylinder motor for a special based on the again relatively common low chassis LWB model. Has it been done ? Imagine a sequential lever and interrupter clutch set up....or am I completely loosing it...Bit off piste for a first post but hey ho !!

Andy

[Ivor Hawkins]

Nothing’s mad when it comes to a special, but that’s quite a lot of horsepower for a seven chassis, plus of course you have to stop it!
Bearing in mind the DVLA points system, you will have changed the engine and gearbox, you may need to replace the back axle and therefore the brakes, so before long you’ll be getting into hot rod territory, but I like the idea!

[austin]

I suppose you could technically say it's the same manufacturer as DIXI was an A7!

[Reckless Rat]

Any compact shaft drive motor cycle engine and gearbox could be made to fit. The K75 is a "flat" engine so you may have problems with getting it to sit properly in an A7 chassis. It will certainly have a bit more get up and go than any A7 engine, and has already been stated your biggest headache will be trying to stop it. If you decide to go ahead please keep us updated with a photographic record of your progress. Such conversions are not unheard of. Someone has fitted a Suzuki Jimny engine in an Austin Ruby and there already exists an A7 special with a Honda CX V twin. SV Ford conversions were "de rigueur" in the day.

I would have thought a Honda Pan European ST1100 V4 would be a better bet...

[Renaud]

I like it too.
If you are prudent with the clutch and the 75 hp power release why not keep the rear axle? And even the gearbox despite losing the sequential? I would use hydro brakes though.
I'm not competent about the DVLA system (who is?) but could that satisfy them?

[dickie65]

I would think a Big Seven chassis would be a better bet as it has beefier kingpins and back axle.
The OHV Reliant engine would be more in keeping though.

[spannerman]

What I say is make your dream come true,
I've built a special based on a big 7 chassis
And a tuned reliant engine I used the big 7
Axle and on rolling road I get 71 bhp at back wheels!
And have found that the axle seems to take it without
Problems only problem I've found is front axle twists
when braking hard ? just.dont build it from a
Restorable car people seem to get upset !
I've thought about fitting a BMW r80 engine think it will
Sound good flat stick on a hillclimb .
Just biuld what you think you like that what makes us
Human doing things different!

[haasad]

Thanks all, so mad but not entirely in my own. I won't be ruining a restorable original car don't worry about that. The K75 is rated at 70 HP but given wear and test is more likely to be 50 or 60. Using its gear box simplifies matters with connection and eliminates a weak point.Im confident in getting it to stop okay with hydraulics. It'll be registered already so I'll declare the engine swap I don't see major problems there. I've done it before with other car builds. The width might be a problem as I don't want to stray too far towards building a new chassis rather than strengthening. I need to do some more work yet to understand those basic matters. Thanks for the positive response. Hoping to get my rolling chassis sorted soon .
Andy

[Reckless Rat]

The only main disadvantage you are likely to encounter is the lack of a reverse gear, assuming that you use the BMW engine/box as a complete unit. Some larger touring bikes do have a reverse facility but I'm sure that is done by using the starter motor rather than the engine (I'm thinking Gold Wing and the big BMW tourer)

[Bob Culver]

hi Haasad
Have you driven a Seven? With most the origianl power available is very adequate for the roadholding.