Imp-engined motorcycle project.

[johnnyboy-wonder57]

Hi,
I'm new to this forum, I'm starting to put together a project of building a Norton-Imp or such like, firstly I am securing the Imp parts, has anyone got any information on a project like this.

I have searched the web and apart from a feature on this site and a fellow called Ken Horwood on an Imp site who built one 30 plus years ago, information is scarce.

The thing that puzzles me is why didn't one of the Motorcycle factories use the ready made adaptable Coventry Climax engines for a new generation of British machines?

They were on each others doorsteps!

Never been without a Bike since 17!

Thanks

Johnnyboy-wonder
Bikes owned:
D10 Bantam;
BSA Shooting Star 441;
Honda CB250RS;
Bikes Still got:
BMW K75S;
Kawasaki Z60 B1;
Piaggio Bravo Moped;

[Goldie]

I have a picture somewhere of an Imp powered roadracing outfit which i took at the St.Eval Roadraces in Cornwall in 1970.

If i find it, i will put it on the forum.

[johnnyboy-wonder57]

Thanks Goldie

Its frustrating trying to get information and one of the Imp sites is down at the moment!  Have you been on the "Engine Punk" website he's down your way, some interesting stuff.

Thought about using a Vincent motor, but you would need a lottery win for that and it would have to be like the ones built down under, benefiting from 50 plus years of technology, but an Imp engine is feasible, light and relatively inexpensive by comparison, thought I would acquire one before they get too rare.  Prices not bad as long as the spec' is moderate, incidentally the 998cc motors are more sought after than the 875cc ones, more tuning potential see.

I have  the beginings of an 875 cc motor and may consider having it stroked out to give it greater flexibility.  With some mods your looking at a power output similar to a 850cc Commando or a T160  which should be acceptable on the road.

May have to go for injection route and so forth, howeverm its all new territory rather than just re-building stock machines Norton running gear would be the match and considering the prices that seem to be being hyped up its cheaper to get a new frame from Andover Norton than secure a genuine old "Featherbed",   £1,400 I ask you for a frame, do they think we are idiots!


Thanks

JBW

[henry_norton]

I used to work with a chap who'd put an imp engine into a featherbed frame in the 70s. The main problems were the weight and the radiator. Although the imp engine was light for a car it was still way heavier than an air cooled twin, especially when you factor in the weight of the cooling system (if you could find somewhere to fit the rad in the first place although there's probably a much better choice of rads these days).

Sounds like an interesting project - there was an imp engined Norton for sale on Ebay a year or so ago which looked really nicely done - I wouldn't mind one  

[VintageBike]

Have you seen the imp at http://www.vintagebike.co.uk/Bike%20Directories/Hybrid%20Bikes/pages/Norton-Imp.htmel

Superb!

Nigel

[johnnyboy-wonder57]

Hi,

Thanks for the replies.
I have managed to trace and contact Ken Horwood and we have exchanged information via email, he also sent me photos of his creation and when he comes back from Switzerland on his German tourer we will continue our dialogues.  Though it  would seem on a solo getting the transmission drive right and using the correct weight of flywheel will be critical to get a correct torque factor  for a standing start.

The whole imp engine transmission unit weighed 172lbs and the quality of the castings are second to none, as far as I understand the were cast by a firm in Birmingham which manufactured aircraft components and have "AM" insignia on them, anybody know any history about this company and if it is still operative?

The inlet manifold has to be felt to be believed "featherweight" is a true description it is an incredibly light-weight component

If you build a side-car unit then the engine can be put in-line like my K75 unit but not horizontal, actually it would be more like the Danish Nimbus motorcycle.  However, I would  prefer a solo machine not having any experience of combinations at this point in time.  In that case the engine is mounted transversely across the frame.

Recently a Featherbed framed Norton with a 500cc Alfin barrelled single engine went for slightly below £1,800.
Perhaps i was slightly out of touch with pricing but last time I looked on Andover Norton site, (I would also be interested in making the rear suspension mono-shock),   you could get a new frame for about £675 but I can't see whether this includes  VAT!

I have also considered using a supercharger, but information  is difficult to get hold of, however because the inlet and exhaust ports are on the same side of the engine  mounting a blower may be easier than first envisaged,
I have seen the Imp -engined Norton on this site and would love to hear from the creators, I believe the bike has been exhibited at a Yorkshire based club show.

Cheers
JBW

[johnnyboy-wonder57]

HI
What kind of money should I look at, for a second-hand slimline featherbed frame, with some of the lugs removed and a V5 document?

Cheers

JBW

[beezaric]

If you want to go fast go find another Honda CB250RS and fit it with an XR500 motor bolts straight in and realy makes the CB go only mods required are exhaust
Ric

[johnnyboy-wonder57]

Ric,
Sold the Honda in 1987 according to dvla, ran till 2001, obviously fast, has a range of interpretations, perhaps my fast is linked to technical innovation without ECU's and includes handling and character, now if I was building a single that would be another story.....

Cheers

JBW

[johnnyboy-wonder57]

Hi,
Right done a lot of research and I was wrong about the side-car mounting like a longitudinal set-up, they were mounted transversely, but not critically mid-centre line as a solo machine would have to be, more and more people state they have owned a Nor-imp but information is still sparse and I would love to hear from anyone, who remembers how they built them and has some photos, I interested in "homebuilt specials anyhow, I still need a reasonably priced slimline frame  and in-particular would like to hear from primary drive fabricators, and those that can cast required parts; as a modified version of ken Horwood's Counter-shaft primary drive is envisaged. Yes, with triplex sprockets and chains and no belts in sight!

Recently met Ken @ a 69 Club bash and guess what, not one old British bike there, as far as I could see, except a Healy square 4 which I missed! Also, & me-thinks that the speculation and inflation of prices will in-effect do to bikes what "they" did to the house market cause it  to go "titsup", if bikes are increasingly too valuable to use then they are of no more use than an antique vase, plus they rust and all the support firms and booming retro-industry will go bust yet again.  If a bike was built to a price and a Turkey when new, no amount of restoration will unmake it a turkey, so to speak.  Just a few thoughts!

I would like to thank, Anna Dixon, Ken and John Flood for their help & advice.

By the way the featured Norton Imp has a few areas of concern the radiator mounting for a start, the radiator hose paths,  the strange angled primary drive-line, but otherwise a magnificent effort, I just hope I can do as well if not better!  Long-live the backstreet builders, for many were better than standard issue machines on the market, hence the Triton e.t.c, also the skills and enthusiasm to do it are fast disappearing as bikes get more like modern cars  with component change technology and untouchable count me out.  I think a Norton-imp is more of a challenge technically too & will hopefully be a successful steed..


Cheers

JBW

[raptorkev]

i saw a norimp once and it looked a right lash up i think it would take a great deal of thought and ingenuity to make it look pukka
on the frame side what about a bsa frame from b31 etc a good solid maybe stronger than the norton frame
but all the best with your project 

[bikerbob]

Hi there
Seen this BSA A10 with an Imp engine at North East show some years ago have been told it is still on the road.

[johnnyboy-wonder57]

Bob,
Difficult to be absolutely sure, but from what i can see it doesn't look like any Imp engine  I have seen, unless lots of mods bolted to it,  but I strongly suspect its powered by something else out of an auto-mobile.


Cheers

John

[bikerbob]

Hi there.
Can only go off what I was told when I asked about it some years ago so if not an Imp engine I really don't know what it is. I really should know because my wife had a Hillman Imp some 30 odd years ago and I bought another one and swapped the engines over eventually the bodywork went and when my wife went on holiday with some friends she asked me to put it through the MOT when she came back It was in the scrap yard and I used the money towards a greenhouse still got the greenhouse.

[johnnyboy-wonder57]

Bob,
here's the bike that I am using as a template in design, Ken Horwood's VPU4S an Imp-engine in a Norton Wide-line frame.  I  have chosen to use a Slim-line frame  and there may be some small modifications outside casting shapes engine canted forward slightly, but essentially the bike will follow these construction lines, integral alternator water-pump in castings, unlike yhe lash-up on ebay last year![







Cheers

John