Converting a 750 to an 850 engine, what does it take?

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Peter Waller

Peter Waller

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I am considering converting my 1972 750 Commando to an 850 /920 and can any one tell me what I would need and how to go about it and anyone who might be able to do it here in the uk?
 
Peter Waller said:
I am considering converting my 1972 750 Commando to an 850 /920 and can any one tell me what I would need and how to go about it and anyone who might be able to do it here in the uk?
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I would think that the cost to convert would be higher then to buy yourself another bike ................. and have two Nortons ;)
 
You asked basically the same thing a little more than a month ago.
www.accessnorton.com

Upgrading a 750cc Commando engine to an 850cc

How hard is it to convert my 750cc Commando engine up to an 850cc? I would really like to do this but do not know what is involved and what new parts are needed. Thanks in advance for any help!
www.accessnorton.com www.accessnorton.com

The answers you received then that it would not be particularly worthwhile should have put you off, but it seems not.
 
PW seems to post a question and then not return to read any of the answers, same with his last post where he never logged on for weeks he has not logged on since Sat to see any answers to this latest post.
 
kommando said:
PW seems to post a question and then not return to read any of the answers, same with his last post where he never logged on for weeks he has not logged on since Sat to see any answers to this latest post.
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Very odd!
 
www.accessnorton.com

Converting from 750 to 850

I've got a 72 Combat that I'm considering converting to an 850. I know I need 850 barrels, pistons and head. Can I bolt the 850 barrels to the 750 crankcase? Anything else I need to know?
www.accessnorton.com www.accessnorton.com
 
worntorn said:
I guess you keep asking until someone says there's nothing to it, bring it here on Saturday morning and we'll change her over while you wait ☺️

Glen
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He can come to my place right now.....our Gite is empty now, only 50€ a night for cash.....

I will explain the answers slowly......as long as he brings the parts to my required parts list.

(though I do have some barrels and a head they will want specialist re-work! As will the 750 cases he brings)
 
Why would you want to make an 850 out of a 750 ? A smaller motor can often be made to go faster then a big one. If you were continually riding in windy conditions, the bigger one might feel better if ou were hitting gusts of wind. A motor which delivers more torque can run higher gearing, but then you are back where you started from, unless you run a close ratio gearbox.
 
acotrel said:
Why would you want to make an 850 out of a 750 ? A smaller motor can often be made to go faster then a big one. If you were continually riding in windy conditions, the bigger one might feel better if ou were hitting gusts of wind. A motor which delivers more torque can run higher gearing, but then you are back where you started from, unless you run a close ratio gearbox.
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It's either bragging rights or for additional torque
I'm assuming he was asking about converting a road bike not a racing bike? Who knows
 
Rather than start a similar thread with I suspect similar answers, i'll post this here:

I'm interested in converting my 2013 Triumph Bonneville to a Norton Commando 850 and can any one tell me what I would need and how to go about it and anyone who might be able to do it in the uk (i'd of course need to ship it there and back :-) ?
 
worntorn said:
If you bring the Triumph by tomorrow morning, I'll have the conversion done and bike ready for pickup by noon. I work fast.
Here's what your converted Triumph will look like-

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Thx, but I know you over charge for your work....like a latte for finder fees etc....too rich for my blood!
 
htown16 said:
Some people want advice and some just want to be told how great their preconceived idea is. Actually happens pretty frequently on forums.
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True, but in this case the original poster never came back to look at any replies, which makes it even odder is he asked same question before and never went back then either.
 
I'm not sure I would want to build an 850 on 1972 750 engine cases let alone earlier 20M3S 750 cases.
It couldn't be that hard though.

A 1974 case 73 mm x 89 mm 750 would be something else and could have been a factory bike with a smaller bore through bolt cylinder.

Perhaps even better would have been a kick start 1975 750 with the Mk3 cases, 3/8" bolt crankshaft and revised for bore RH10 cylinder head.
Lively and free revving within reason in candy apple red.

If if's and but's were candy we would all have a merry Christmas.
 
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