Work Case #16 CRF450R

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Thedktor
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Work Case #16 CRF450R

Post by Thedktor » Sun Mar 29, 2020 7:34 am

Previous #15 Montesa Honda Trials Bike


Work Case #16 CRF450R
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Now you can’t really see from the photo but this is a “road legal” CRF450 MX bike with number-plate, lights, horn and a speedometer!

So, why would you do this? Well its a good question but a modern 450 motocross engine is quite something, and without noise and emission restrictions are phenomenally powerful in a very light chassis. This does make them very demanding to ride on a MX track as the power starts right from the bottom, with instant response, and they are far too much for most riders, but when the next size down is only a 250 the 450s keep on selling.
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We did a handful of these conversions and they worked better than you might expect. This engine is reasonably refined, and with fuel injection pulls cleanly from idle within the limits of its light flywheel. However, the main problem with MX bikes is their tall first gear, and raising the gearing as part of this conversion does make it too high for normal trail riding for sure. For hooning around on the road not a problem.

Talking of which - I was able to give one a proper road test after it was run-in and holy moly it made even a 300 2 stroke seem quite tame! :shock: :shock:
On the road it was actually quite controllable but effortlessly powerful, 70 came and went, and the front wheel lifted at every opportunity! :P

Loads of low end but with a very high rev ceiling and over-rev as well, there for racing of course. An incredibly flexible and usable engine, just not very practical....

Next #17 Husky FE450
Last edited by Thedktor on Wed May 27, 2020 6:36 am, edited 1 time in total.
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cozi70
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Re: Work Case #16 CRF450R

Post by cozi70 » Sun Mar 29, 2020 9:23 am

What sort of service intervals and hours usage/rebuilds/mileage are expected from these engines?

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Re: Work Case #16 CRF450R

Post by Nico-D » Sun Mar 29, 2020 12:14 pm

Interesting, sounds a proper hooligan bike :D
I was wondering why you wouldn't start with the 'X' enduro version to make a road legal one ? It has a wider spread gearbox and heavier flywheel surely ?

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Re: Work Case #16 CRF450R

Post by Mad Hatter » Sun Mar 29, 2020 12:51 pm

Nico-D wrote:
Sun Mar 29, 2020 12:14 pm
Interesting, sounds a proper hooligan bike :D
I was wondering why you wouldn't start with the 'X' enduro version to make a road legal one ? It has a wider spread gearbox and heavier flywheel surely ?
That's exactly what I was wondering.

I've ridden both made road legal, the X seemed a little better for trail stuff but as far as I remember the clutch on both was nowhere near as smooth as my KTM at the lever.

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Re: Work Case #16 CRF450R

Post by Thedktor » Mon Mar 30, 2020 7:56 am

I don't think the people that bought these bikes were the typical trail riders that we might recognise, more like MX riders who wanted something to just hoon around on for 1/2 hr and then leave it in the shed for the next six months....

Can't recall the service intervals for the Hondas, hardly any MX bikes came back for any servicing, obviously being done cheaper elsewhere.

The Husky/KTMs MXers required new pistons at 40 or 50 hours, under race conditions. Not because they were worn out but as a safety measure. The little 80 and 125s it was just 20 hours! But they were at max revs constantly.
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Re: Work Case #16 CRF450R

Post by Mad Hatter » Mon Mar 30, 2020 10:44 am

That's a good point, different strokes for different folks. I know the fuelling and the mapping is different on them as well as the gearbox so maybe more usable for something that isn't trail riding, I know there's a relatively active scene for supermotos on go cart tracks so maybe the much longer first gear is suited to that more, like you said effortless power on the road.

As fair as I remember the service intervals on the x series ones are pretty similar to most ktms, but as you said for race conditions. I was looking at the 250x's when I got my 450 KTM, it all came down to price in the end and I got my 450 cheap because it was a shiter but road registered.

I pulled the top end on mine after I'd used it for over 50 hours with a couple of races on it, some trail riding and a 5 day trip to Wales with camping kit as it was second hand and a dog, in all honesty it looked fine I was just getting into it anyway to check as I was already replacing the cam chain, rocker shafts and rocker arms. I think a previous owner had already done the piston but bugger all else and I had no idea how many hours were on it after someone removed the Speedo/hour meter :lol:
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Re: Work Case #16 CRF450R

Post by bowber » Tue Mar 31, 2020 8:04 pm

My 400exc had over 10k on it when I took it to bits, the piston rings were over 1mm gap and the inlet valves were knife edged, still started and ran fine. New piston, rings, inlet valves and cam chain and it's been no problem for the last 2k or so.
The bore and valve seats were perfect as well.
Before I bought my 400 as a project rebuild I'd been looking at the 450X but I decided the early ones sounded like they needed a bit more work than an old RFS KTM in the price range I was looking at.

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Re: Work Case #16 CRF450R

Post by Ksithumper » Tue Mar 31, 2020 8:17 pm

By way of comparison, my lad's 701 Husky had over 820 hours on it, before it was nicked recently.
The dealer had the lid off at 700 hours, all good. (changed a cam chain as a precaution, given we were already in there).
Clean oil and filters boys - the air filter is even more important than the oil fillter

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Re: Work Case #16 CRF450R

Post by Thedktor » Sat Apr 04, 2020 6:43 am

Ksithumper wrote:
Tue Mar 31, 2020 8:17 pm
By way of comparison, my lad's 701 Husky had over 820 hours on it, before it was nicked recently.
The dealer had the lid off at 700 hours, all good. (changed a cam chain as a precaution, given we were already in there).
Clean oil and filters boys - the air filter is even more important than the oil fillter
Hours? What's that in miles then. The 701/690 is of course a much more robust engine design to the EXC's , with just the odd problem with cam followers and balancer shafts to worry about ;)
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Re: Work Case #16 CRF450R

Post by dibbs » Sat Apr 04, 2020 8:30 am

Thedktor wrote:
Sat Apr 04, 2020 6:43 am
Ksithumper wrote:
Tue Mar 31, 2020 8:17 pm
By way of comparison, my lad's 701 Husky had over 820 hours on it, before it was nicked recently.
The dealer had the lid off at 700 hours, all good. (changed a cam chain as a precaution, given we were already in there).
Clean oil and filters boys - the air filter is even more important than the oil fillter
Hours? What's that in miles then. The 701/690 is of course a much more robust engine design to the EXC's , with just the odd problem with cam followers and balancer shafts to worry about ;)
I reckon thats about 22000 miles!

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