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How much does it cost to build a vintage mx racer?

For many years I've wanted to have a go at twinshock racing - I always wanted an MX bike when I was a kid but couldnt afford one. A few years ago you could pick up a complete twinshock racer for a few hundred quid. Note the word complete, that doesnt mean running or even in one piece. Complete means at least you get all the bits, which is important because one thing you do realise when you start rebuilding bikes is that every model has its weak spot and those bits get more difficult to find as bike gets cannibalised for parts.

This example is our 1975 Honda CR125m, a project bought some 10 years ago for £400. The bike was complete and even had some nice extras, a red line box section swing arm for example. So, how much money did it take to get the bike onto a track? Everything we spent is listed below, prices arent adjusted for inflation!

Purchase Price: £400

Spares Bike: £79 (1976 CR125M) - proved its worth as the electrics from the original bikes were shot, but this bikes were in great condition. Alot of the other parts didnt fit as quite a bit changed between 75 and 76 (e.g. the airbox)


  Cost Postage Notes
Chain Guide 90.55 26 new spring loaded chainguide - required to fit Red Line swingarm, and upgrade on the fixed roller of the original bike.
plastics 90 26 from DC plastics in America - only the side panels, not the greatest quality and didnt fit too well due to the fact that extra strengthening panels welded in to the frame
front brake arm 29.99 4.99  lost the original one...
parts manual 6   not really necessary now as there are plenty online
carb rebuild kit 20   cheap Keyster kit
Kickstart 20 16 original had been badly welded in the middle
Kickstart Spindle 30 34.05 original had been sawn off at some point so kickstart wouldnt stay on...
fox shox 40   cheap pair from DK spares which required full rebuild and shafts rechroming
tyres 100   Michelin Starcrosss Medium compound from Demon Tweeks
rear brake lever 24.99 15.01 original was a dodgy pedal off something like a honda cub...
brake pads 30.56   linings had separated from the original brake shoes
front brake cable 17.05   original was seized
gasket (head) 0.99 1.5 bargain
crankshaft 106.5 41.95 at the time you couldnt buy rod kits so the only option was to buy a reasonable crank - expensive to ship from the states
Inlet 63 12.95 the one fitted to the bike had perished and had be sealed at some point with silicon sealant
Conn Rod 45 21  got ripped off by someone claiming to have a good conrod - turned out to be useless, hence the new crank
piston 33 2.5 brand new piston from David Silver to go with rebore
wheel rims 150   Both wheel rims were cracked so we purchased some Excel rims as we were looking for race worthiness and not originality
bearings/seals 100   ordered a kit, didnt include all the bearings - there is needle bearing in the engine that is no longer readily available
gasket kit 12 2.6 original honda item
airbox connector 13.35 2.34 bike didnt have an air filter when purchased
fox rebuild kit 11.5    seals for the Fox Shox
M3 bolts 1.89    
filter foam 7.5   couldn't purchase a filter (none for the 75/76 at the time, later models available) so had to make one
chain 19.99    
spring fastner 4.32    exhaust springs
overflow pipe 3.55    
fuel pipe 4.25    
circlips 1.9    
thread repair 5.59    drain bolt on fork slider needed repair
M8 x 60 bolts 2.35    
M10 x 50 bolts 2.29    
M4 pan head bolts 1.01    
M4  (14mm) 1.99    
circlips 1.9    
spark plug 11.3    
kill switch 9.9    cheap alternative to the original switch which is no longer available
oil 12.9    
Throttle tube 26.95 15.76  exisiting one was badly cracked and wouldn't rotate
washers 20 14.5  
piston pin, needle brg, piston clip, woodruff key 29 14.5  
seals and bolts 31.5 13  
total £1234.56 £339.65  



type Cost Postage  
paint 30 5 tank was a mess and I decided to repaint it, originally in just plain silver, but eventually in the correct colours. For 1975 that means Tahitian Red on the top of the tank over a silver base. We made the decals.
POR 15 16.99   As soon as I started to clean the tank (it was corroded inside) by filling it with vinegar it started to leak. Hence this was required to seal the tank.
wheelbuild 100   We tried to rebuild the wheles, but sadly after a good few attempts wew had to admit defeat and have them rebuilt professionally
rebore 30   bore had some scoring, but was within the tolerance for a rebore and oversize piston
fork rechrome 170   Forks were both bent and rusty
shaft rechrome 100   replacement shafts for the early shocks (which have jets on the end) aren't available so these needed to be rechromed
total £446.99  £5.00  

So the grand total is £2500.20 and that doesn't take account of the time taken!

I can even think of a few things that I don't have the receipts for (seat cover, handlebars, clutch lever), but this is what it gets you:

Honda CR125M 1975 Elsinore


The things that struck us when we added this up was how much we spent on postage and how much more we could have spent if we'd been looking for a nut and bolt perfect restoration. Hvaing done the bike a lot has been learnt about what to look out for when buying a bike. Completeness is one thing, but are all those bits serviceable? Having said that, at least we know whats been done inside the mootor and that the suspension is race ready. Having rebuilt the engine completely with new bearings and seals it fired up and ran easily - it took a bit of fettling to get it running smoothly but that keep in mind that this bike has obvious;y had quite a few mods made to it over its lifetime and therefore reverting to original jetting etc was probably not a great idea given the custom pipe and probable porting of the cylinder.