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529
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11/5/2015
Location
DK
Fantasy
2963rd
Edited Date/Time
6/16/2020 9:43pm
Hi!
I'm able to get a very cheap RM125C rolling chassis, so I thought about shoehorning in a 4 stroke engine of that era.
The only rules are that it has to be pre-85 and air cooled. I'd prefer a wetsump.
Which model would you choose?
XT500 has a large aftermarket following which seems nice. Though Hondas XL500 could work too I guess. I've ruled out Husqvarnas due to price and availability.
I'm able to get a very cheap RM125C rolling chassis, so I thought about shoehorning in a 4 stroke engine of that era.
The only rules are that it has to be pre-85 and air cooled. I'd prefer a wetsump.
Which model would you choose?
XT500 has a large aftermarket following which seems nice. Though Hondas XL500 could work too I guess. I've ruled out Husqvarnas due to price and availability.
79 / 80 model, almost the same.
The Shop
I think the XR200 will be out of the question, as they weren't really a thing in Europe.
I have one in a 1980 RM 125 frame. Hi comp piston, mid range cam and oversized exhaust and it is more fun than most of my bikes.
The 200 engine is easy to find over here and since you should be building back up from the cases upward, start with a good bottom end and then source the rest. Easier to ship over and then you would also know the history of the engine.
I am 6’4” and 225 and the bike never feels underpowered.
Oh, and it is much lighter than my HL 500.
He also built a 1980 XR200.
I will post a link to a build of another 1980 XR200 made to
look like a mini HL 500 by a regular joe who’s only advanced skill is basic welding. It is a step by step instruction thread if you want to build your own.
I should be able to post it by tonight.
I'm on board with putting in something similar to the XR200. I tried fitting in an XT500, but it was just way too big for the frame.
Over here, XL185 engines seem plentiful compared to the XR200. Can I make the 185 run like a XR200.
I'd need to overhaul the engine anyway, so boring out a cylinder and changing cams is not going to matter that much.
Here's a couple of pictures of what I'm starting with.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&ved=0CD…
From there the engine will bolt in with fabricated and welded mounts.
The kick start action will be the biggest head ache.
As I said two steps forward and one step back!
But yes, making a new cradle will be a neccesity.
Did you look at Alan Steele YouTube site?
Pit Row
Do you know the height of the engine? I'd consider an SP370, if they aren't too far off.
EDIT:
Checked Alan's YouTube, great stuff, perfect for what I want!
An xl185, hi comp, big bore, stroker, head work, big cam, big exhaust, pumper carb with a light flywheel should have enough go for a 59 year old squid.
Here's an absobloodylutely lovely 79 RM125 chassis with 99 XR200 engine - I think I snaffled these pictures from this site.
A big advantage of an XR200 engine over the XL185 is the 6 speed gearbox.
I ran a much modified XL engine for quite a few years, until I got a 6 spd XR. That extra gear, made it So Much Better.
I'm currently just keeping an eye out for an 'as good as I can get 230' engine, for the E Start. Just because my leg doesn't even bend to 90 degrees, nowadays. I also had to run an MVX 250 (Honda 250 2stroke 'V' Triple - look it up!) Kick Start lever, which was hard to deal with, on the 89 CR Chassis I last used it on, and, which necessitated my making an ATK style rearward facing rear brake lever and master cylinder set up.
I'll transfer my top end to the ES'd cases, with it's Big Fins I put on, Oil cooler set up (with high capacity TLR250 Oil Pump - the body and pump gears are about 2 / 3mm wider than the early 200 engines - later models may be near that, as I've seen a few different Oil Pump body and gear part numbers in later model parts fiches) , and TLR 250 barrel. All those fins make the unknowing think it's a much bigger capacity engine
That was enough to consistently beat blokes on all sorts of XRS Only 280s and 630s, and the (inevitable) wankers on 4t Huskies. Though, I had to ride so, so bloody hard to win, or place, and I'm very far from that level of riding / risk taking now.
It was a fantastic little bike, in both chassis I ran it in, a real 'sleeper', but, with that massive (I'm being facetious, boys and girls ) power output (well I think a std 200 had around 13 / 14 HP) , it started snapping the main shaft, and counter shaft, plus, exploding the 3/4 (I think that was it) gear combination. Long ago I had the gears and both shafts made by a specialist manufacturer, but it's all sitting in the cupboard / shelf that this computer is on, with the 83 RM125D chassis, and the 89 CR125 chassis I mentioned previously, both hanging from the workshop wall. All waiting for me to put either combo together. There's a chance of that, what with EVO racing and VMEnduro being pretty big now , but I've got so much else to do in my semi retirement
A Key thing with engine placement, is the Countershaft position. Replicate the position of the std engine / countershaft!
Not doing so Will stuff up handling / the suspension. I know this, as I first buggered it up with other conversions in my youth. By having it too high, because I left a std cradle in place. And, even that beautiful bike I put pictures up of, above, looks to have that serious mistake - look how high the CS center is, with relation to the Swing Arm pivot, and the rear axle.
Even something as mildy powered as a 'worked' 200 engine, with the countershaft too high, will have so much pull down effect on the rear end ( magnified by the high revs you'll be constantly using because it's so under powered) that it will not work as well as it could do, if you positioned the engine correctly.
I bought a damage engine, so I will aim for getting a 6 speed gearbox and a CB100 ignition.
Are there any sensible engine mods, which will still retain some reliability. I don't want to go all out , neither do I want 13/14 hp.
I looked into it although I eventually gave up and got an xr185 flywheel which looks to be maybe 20% lighter than stock.
There is so much cross over of parts it would boggle your mind.
Along with the much copied horizontal 'Cub' engine ( which, in 2017 reached a benchmark of 100 Million made - the highest production of any vehicles series, ever), in all it's sizes, and the 70cc through to 110 / 150(?) engines, and this basic engine, I reckon those few engine modules have made for a significant part of Hondas profits, and their 'bank balance' to do so much of their development of the rest of their bikes, cars, and their racing.
Even with the change over to the 'new' 230 EFI engine in CR-fs, which I think is made mostly in Hondas vast Brazilian factory, but probably also in a bundle of their other plants around the World, the older 100/125/150/185 / 200/ 230 engine is still used in many, many thousands of bikes Honda produce. Quite amazing, really. It's a heck of an ROI.
Good luck on your 4 stroke project though, they must be a blast to ride !
Lots of talk but have yet to come across an actual completed ignition.
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