Posts
613
Joined
11/5/2015
Location
DK
Edited Date/Time
7/28/2022 2:38am
For as long as I can remember, I’ve wanted a four stroke classic motocross bike. However there aren’t many around, sure you have the Husqvarna TC510, but they are very rare and expensive, spareparts even more so.
So converting an XT engine was the next thought. Like a HL-replica, great idea, immense amount of work. Now I am not a great fabricator, so I ruled that out if I was to ride it in this lifetime.
Then one night I stumbled across a site by a framemaker in Holland. Only thing was money, and I had none. So eventually I scrapped the project and found a YZ250 from 1981. The thought still lingering I decicded to sell it and use all the money on a BZS frame. I could choose between the XT500 and XR500.
I chose the XR500, as it seemed like the better base and the XL500 was very popular in Germany, so cheap spares and engines are readily available.
Pictures will follow!
So converting an XT engine was the next thought. Like a HL-replica, great idea, immense amount of work. Now I am not a great fabricator, so I ruled that out if I was to ride it in this lifetime.
Then one night I stumbled across a site by a framemaker in Holland. Only thing was money, and I had none. So eventually I scrapped the project and found a YZ250 from 1981. The thought still lingering I decicded to sell it and use all the money on a BZS frame. I could choose between the XT500 and XR500.
I chose the XR500, as it seemed like the better base and the XL500 was very popular in Germany, so cheap spares and engines are readily available.
Pictures will follow!
Today I dissassembled the engine. I was pleasantly surprised by the condition. No stripped threads or other worn parts.
I'm now contemplating what to do with the cases, cylinder and head. Dryice blasting and painted black or vapourblasting?
The Shop
Luxon 4-Post Bar Mounts
$189.95 - $239.95
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
I have my third and last GMC HL 500. Also a few XR 200 builds, one in a 1974 Ossa Phantom frame and another in a 1980 RM 125 frame plus a highly modified 1991 XR 200.
I want to buy my buddies HPF XR 500, but I think a new frame and built without the Fox sw/shocks/fork will keep my costs down and the new metal used in the frame will be more reliable.
I can’t wait to see more.
Following pictures show the lower steering stem bearing exposed. It seems like there should be a collar sealing against the sealing ring.
A mate of mine got one a couple of years ago, after harassing me to make a C&J copy for him for many years. I Don't do copies, I've too many things of Mine to make.
Anyway, he brought it to me for the build up, and to have a few things done, like the pipe build.
The B.Z.S is a lovely done kit, but I think they must get the apprentice to weld on the inner shock mount plate to the seat rail - his welds at that area looked exactly the same, like they didn't have a foot ( or, a finger throttle - I'd like to try one for my crawling around in tubular car chassis building, it would make things a bit easier on this old bastard) pedal to back off on the amps as the tube and plate got ever hotter. Nothing terrible about it, but it's interesting to see on chassis that may have a few years between them.
A little extra thing that I did do was to put at slight angle and tiny radius on the top reinforcement plate on the swingarm, at the forward point. As small as it was / still is, it seemed so unfinished to leave that squared off / right angled corner edge. I know, a bit bloody pedantic, but, just getting rid of that made me happy. I haven't seen an original C&J frame for decades ( where I worked in the late 70s early 80s, we brought in C&J and other frames from the USA ), so maybe it was how they were made?
Should be a beautiful thing, and with the right suspension set up, and Good brakes, you can give blokes on modern bikes, a bit of a hurry up. Old Thumpers, are pretty effective, so long as you don't ride them like a modern day 4t - as in, ( Not) revving the guts out of them.
Pit Row
Yes it is a BZS frame in question. Some nice assessments you made there, I will have a look at the points you pointed out.
For now I think I will have a collar made to cover the lower steering stem sealing ring and at that also have the steering stop.
The B.Z.S chassis is a lovely thing. I'm not knocking it at all.
So, what Forks are they that you will be using, and what shocks? You've got to be careful with any Piggy Back Reservoirs, and their adjusters, if any. The shock rotates away from the SA pivot to shock mount rail, and Up towards the seat rails. And, the RH side has the pipe routing that can ad to clearance issues.
Oh and what tank? I put what I think was 450 / 480? (2T) tank on his bike, as I had a few lying around - I've no idea how they came into my possession
Do you know what brand of shock you are going to be using?
You might want to look at their specs to verify you will be getting the travel you want/need.
Race Tech and Noleen in the USA are very astute in these calculations.
For tank I bought a CR250 Clarke tank, which has yet to show up.
I've a decades long association with Fox Suspension, with having worked at Australia's first Fox Importers in the 70s / early 80s, then using them on my MTB DHers, then being the Fox Tech in OZ for many years. And now, with my (thinking of) getting back to making more than just a few DH / Enduro frames a year, to perhaps a few handfuls, I'm still using Fox products by preference.
But, I have no illusions about how 'good' the Fox (Motorcycle) Airshocks are. I've a few pair, still, along with some emulsion shocks, Fox Factory Remote resi shocks, and Dual shock / Single shock Twin clickers, and my set of 44s.
Some of my friends at Fox have made up modern Airshocks, using their ( well, mixed parts of) Quad, Snowmobile and ATV shocks. And They, have been very, Very impressive. I don't know if they have ever offered such units for sale for the VMX market. They really don't care much about the Motorcycle side of things anymore. Understandable considering how tiny a market it is, in comparison to other markets for them, but, I find it a bit sad.
I've no idea what the valving system is in the Vintcos. I'd like to think they may have been internally changed to a more modern design, but can't find info as to that.
As an aside, I've been impressed by the performance during the few rides I've had on the Thai made YSS externally adjustable shocks, on some VMX bikes. And, they appear to be quite well made, and reliable.
It appears that you are going to have to source either spherical bearings for each eye of those Vintcos , or get shocks that take them.
I'm not 100% sure, but I think my mates BZS had the canted top shock bolts as it appears to be the case with yours. And, again, I'm unsure, but it was to deal with the top mounts being narrower than the swingarm mounts. Much like the last versions of the Twin Shock Huskys. Unfortunately, the BZS chassis bike, is a long way away from me, and, the owner is in Britain, working. Not that he'd have much of a clue as what is on the bike - he's a 'buyer', not a 'builder', and the most inept mechanic I've ever come across. But, he makes a fortune, he has others, to do his 'things'. Fair enough, money makes the World go around, as they say.
He has about 4 sets of shocks for it, ALL having spherical bearings in each eye. One set was a pair of original Ohlins ITC ( the Blue, 18.5 / 18.6" . 470 /475mm eye to eye ) that I made new, shorter shaft eyes, to bring them to the correct length. The Shaft Eyes on the last model Twin Shock Huskys, were extended to go onto the Outside of the swingarm, and, they canted in up to the top shock mounts . They were used only initially. He has since obtained sets of Falcon Shocks, a pair of YSSs, and modern Ohlins, all with external Rebound and Compression adjustability.
I note that the Vintcos list the eyelet reducers / spacers they supply as being 10 x 12 x 16mm. And, pictures seem to show an insert in the eyes, that could be a DU bushing - is that the case? You might have to do a bit of searching for spherical bearings, or, perhaps have the shock eyes machined out to fit what is available. Generally, freely available spherical bearings with 10mm centers, have an O.D of 22mm, but, I've come across smaller OD ones, but they tend to have Very narrow outer diameter Widths, that could easily 'punch' into alloy housings / eyelets. I wish I could help with the spherical bearing options better, but, as I said, I can't currently get to the bike, or shocks, in question.
Post a reply to: C&J XR500