My Can Am 250 TnT project bike
When I was a motocross mad kid in the late 70’s my bedroom wall was plastered with pictures from Trials and Motocross News and Motocross Action. One of the bikes I remember was the Can Am MX 1’s and 2’s. I think that the shape of the tank and the colours of the decals combined with the extra brace on the frame made them stand out from the rest.
So fast forward to last year I saw the project come up on Ebay, and after a bit of research I realised that the Army bikes were pretty much TNT 250’s, which themselves are very closely related to the early motocross bikes. The main differences are the Army bikes have 19 inch front wheels for some reason and a large capacity fuel tank. Mine was an incomplete box of bits that needed a full rebuild.
So the first task was to start stripping off all the green paint, so I thought it would be a good idea to make a bead blast cabinet to hook up to my compressor, and this worked well and was a godsend to be honest. I also researched electroplating and invested in a small hobby nickel plating kit for refurbishing small items.
From now on Ebay was my friend and I managed to pick up a 21inch Akront front rim and an Alloy one for the rear to replace the rusty steel one, with the all important 40 spoke holes which is quite unusual nowadays.
A word of thanks
At this point I must express my gratitude to Chris at canned-ham.com for his generously given knowledge and for putting the wealth of information on his website – Top Bloke. I must also thank Richard at canamclinic.co.uk for providing lots of hard to find parts.
My expenditure was ramping up alarmingly, but the single biggest cost was the fuel tank. I ordered one of the Clarke reproduction tanks which is brilliant but by the time import duties were added came to a whopping £280 plus 50 for decals…Ouch, but once I dropped it on the frame it was really worth it. Everything was starting to come together now.
The quest for power
From an early stage I wanted to get the power up from the Army bikes modest 26bhp. As the Rotax engine is a disc valve you can trim the valve to let more air and fuel in, Canned Ham website has a template for this. I also cleaned up all the casting marks on the cylinder with the trusty Dremel tool, not exactly Stan Stevens standards, but a big improvement on the original. Thinking back to my days in the RAF I remembered that all NATO vehicles were designed to run on the most basic of fuels in any given country eg 92 ron. To run this low octane fuel the compression ratio must be pretty low, and reading through the manuals I needed a new cylinder head, luckly I managed to find one, and after a quick check we were back in business.
Will it start after 22 years
We were now rapidly approaching the first start up……but no spark was present, bugger! A quick look on Richards website pointed me in the direction of the charging coil, which was confirmed with a resistance check on the fluke. I managed to find a chap locally who was able to rewind the original coil for me – result a nice fat spark, lots of compression and fuel – lets give it a go…..wow started 4th kick after not running for 22 years. Maybe there is something in the rumour that these Rotax engines are bulletproof.
As the tank and decals were looking so good I decided I really needed new mudguards to finish off, so these were ordered from the states. I really wanted to stay as close to the vintage motocross look as I could, so decided to go with a daytime only MOT which would allow me to run without lights. After a final check over it was time for the test and it went through first time. I also had a chap come over as I was waiting tor the test who commented how good the bike looked, which was really nice – thanks.
I’m really enjoying riding the Can Am around the rural Lincolnshire lanes, and there is a new project on the go…..A Yamaha IT400 street tracker conversion, but more about that later.