4-stroke VMX conversion, ideas/suggestions

project racer
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project racer 1/15/2020 3:25pm
1/15/2020 3:25pm
An RFVC XR250 engine would be nice.
1
inthebadboycorner 1/15/2020 4:55pm
1/15/2020 4:55pm
Google, Ozvmx forum, " Best way to make an xr200 a mid field gun".
XRM200#8
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XRM200#8 1/20/2020 7:09am
1/20/2020 7:09am
Bearuno wrote:
[img]https://p.vitalmx.com/photos/forums/2020/01/07/396758/s1200_1979_RM125_frame_with_1999_XR200_Engine_RH_side.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/01/07/396759/s1200_1979_RM125_frame_with_a_1999_XR200_engine_LH_side.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/01/07/396760/s1200_1979_RM125_frame_with_a_1999_XR200_engine_RH_side_from_forward.jpg[/img] Here's an [i]absobloodylutely [/i] lovely 79 RM125 chassis with 99 XR200 engine - I think I snaffled these pictures from this site. A...




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 Whistling With a stroker crank, machined heavily for lightness, plus the flywheel machined right down, the bigger inlet valve, porting, 32mm carb and Megacycle 'Curtis Sparks Flat Track' spec cam, it revved to the moon (despite the 66+mm(?) long stroke), and dyno'd out to a whopping 28/29HP. Woohoo I tried to run it as a 249cc, but it became prone to seizures with such near paper thin cylinder walls, so sleeved the TLR barrel back to the 200 sized piston.

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 Dizzy .

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.
Hi Guys,

These pics of my XR/RM conversion was my first go at it. I had to make several changes from this version to get it to work, I had to basicly start over in the motor placement, Had to extend the front down tube 2 inches and straighten the lower frame rails and reattach them. this allowed me to lower the motor in the frame and move it back so the counter shaft swing-arm relationship was closer. by doing this I had to build a new brake pedal and mount it from the outside because lowering the motor took away the clearance for the pedal to run under the motor.

This was almost a year long project gathering parts mocking up and redoing things to get it the way I wanted it. This wasn't my first bike to build but was my first making a motor fit a frame that it wasn't built for so it was a learning experience for sure. I have attached a few more pics to see the where it is now.




4

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XRM200#8
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XRM200#8 1/20/2020 10:13am
1/20/2020 10:13am
Bearuno wrote:
[img]https://p.vitalmx.com/photos/forums/2020/01/07/396758/s1200_1979_RM125_frame_with_1999_XR200_Engine_RH_side.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/01/07/396759/s1200_1979_RM125_frame_with_a_1999_XR200_engine_LH_side.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/01/07/396760/s1200_1979_RM125_frame_with_a_1999_XR200_engine_RH_side_from_forward.jpg[/img] Here's an [i]absobloodylutely [/i] lovely 79 RM125 chassis with 99 XR200 engine - I think I snaffled these pictures from this site. A...




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 Whistling With a stroker crank, machined heavily for lightness, plus the flywheel machined right down, the bigger inlet valve, porting, 32mm carb and Megacycle 'Curtis Sparks Flat Track' spec cam, it revved to the moon (despite the 66+mm(?) long stroke), and dyno'd out to a whopping 28/29HP. Woohoo I tried to run it as a 249cc, but it became prone to seizures with such near paper thin cylinder walls, so sleeved the TLR barrel back to the 200 sized piston.

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 Dizzy .

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.
Hi Bearuno,

Agree 100% on the motor placement. The above pics were my first stab at this. was terrible!!!!

Here is a couple pics as it is today.

3
RF145
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RF145 1/20/2020 10:41am
1/20/2020 10:41am


Here is a local build, a Mini HL500, HL200.
I have been looking for the link to this build as it was well documented.
Hopefully soon.
4
XRM200#8
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XRM200#8 1/20/2020 11:09am
1/20/2020 11:09am
RF145 wrote:
[img]https://p.vitalmx.com/photos/forums/2020/01/20/399266/s1200_50E0DAD3_7758_4B72_BC43_E740E2CEEBF3.jpg[/img] Here is a local build, a Mini HL500, HL200. I have been looking for the link to this build as it was well documented. Hopefully...


Here is a local build, a Mini HL500, HL200.
I have been looking for the link to this build as it was well documented.
Hopefully soon.
That bike was built in New England somewhere and is in Arkansas now, I saw it at Diamond Don's this past year. It was one of the builds i looked at and got some ideas from but also some i avoided
1
RF145
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RF145 1/20/2020 10:15pm
1/20/2020 10:15pm
XRM200#8 wrote:
That bike was built in New England somewhere and is in Arkansas now, I saw it at Diamond Don's this past year. It was one of...
That bike was built in New England somewhere and is in Arkansas now, I saw it at Diamond Don's this past year. It was one of the builds i looked at and got some ideas from but also some i avoided
If Westchester County NY, 10 miles North of NYC, is New England, then sure.
Lasse
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Lasse 1/21/2020 5:12am
1/21/2020 5:12am
I've sold the project because I found a better donor.
1
XRM200#8
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XRM200#8 1/21/2020 5:50am
1/21/2020 5:50am
XRM200#8 wrote:
That bike was built in New England somewhere and is in Arkansas now, I saw it at Diamond Don's this past year. It was one of...
That bike was built in New England somewhere and is in Arkansas now, I saw it at Diamond Don's this past year. It was one of the builds i looked at and got some ideas from but also some i avoided
RF145 wrote:
If Westchester County NY, 10 miles North of NYC, is New England, then sure.
Ahh! Here is the link

http://acrmxscoring.com/Forum/snitz/pop_printer_friendly.asp?TOPIC_ID=1…

1
XRM200#8
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XRM200#8 1/21/2020 5:58am
1/21/2020 5:58am
Lasse wrote:
I've sold the project because I found a better donor.
Oh No! Sorry but hope your new project goes well.
1
Bearuno
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Bearuno 1/22/2020 2:10am
1/22/2020 2:10am Edited Date/Time 1/22/2020 3:57am
XRM200#8 wrote:
Hi Bearuno, Agree 100% on the motor placement. The above pics were my first stab at this. was terrible!!!! Here is a couple pics as it...
Hi Bearuno,

Agree 100% on the motor placement. The above pics were my first stab at this. was terrible!!!!

Here is a couple pics as it is today.

Thanks for taking my posting in the way you did.

I made a mistake with my earliest conversion as a sallow teenager (back in the 70s) even as I realized as I was doing so, I'd royally stuffed up.

My Dad and Uncle, both inveterate tuners and 'specials' builders, just sat back, and let me stuff up - sounds harsh, but you learn the most, from your mistakes.

I go on a fair bit about duplicating the Counter Shaft Center to Swingarm Center and Rear Axle / Swingarm Angle / Drop, with so many threads all over the net. Some get really upset, just clinging onto "I made it (or, more often, paid for it to be done), so it's perfect' mindsets. I just want to help people really end up with a great working bike. You can't always get the same position, but you can always get bloody close. Sometimes, you can actually improve upon the original engine / frame combos kinematics.

I've done many, many conversions over the years, and have made Bicycle and Motorcycle frames for over 4.5 decades. So, I do tend to have a bit of a "it's easy" attitude. But, I always say, to show my limitations: well, if my computer goes 'ping', you'll find me in a corner in a fetal position, not having a clue as to what to do. My knowledge / skills, are quite 'analogue'.

Correct motor positioning is absolutely Key, and I try to emphasize that, and Not doing conversions to make the 'ancillaries' (like pipe mounting / electrics mounting / air box etc) easier. Those ancillaries Are, at times, bloody difficult to do, but a bit more work, and owners can end up with a truly great bike.

Your bike, is bloody Gorgeous. Cool I'll be saving those later pictures you put up, to put with the rest of the pics I have of it.
3
Steve F
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Steve F 1/22/2020 5:05am
1/22/2020 5:05am
Man, I have to build one of these!!! Love it!!
inthebadboycorner 6/16/2020 9:43pm
6/16/2020 9:43pm
Bearuno wrote:
[img]https://p.vitalmx.com/photos/forums/2020/01/07/396758/s1200_1979_RM125_frame_with_1999_XR200_Engine_RH_side.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/01/07/396759/s1200_1979_RM125_frame_with_a_1999_XR200_engine_LH_side.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/01/07/396760/s1200_1979_RM125_frame_with_a_1999_XR200_engine_RH_side_from_forward.jpg[/img] Here's an [i]absobloodylutely [/i] lovely 79 RM125 chassis with 99 XR200 engine - I think I snaffled these pictures from this site. A...




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 Whistling With a stroker crank, machined heavily for lightness, plus the flywheel machined right down, the bigger inlet valve, porting, 32mm carb and Megacycle 'Curtis Sparks Flat Track' spec cam, it revved to the moon (despite the 66+mm(?) long stroke), and dyno'd out to a whopping 28/29HP. Woohoo I tried to run it as a 249cc, but it became prone to seizures with such near paper thin cylinder walls, so sleeved the TLR barrel back to the 200 sized piston.

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 Dizzy .

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.
XRM200#8 wrote:
Hi Bearuno, Agree 100% on the motor placement. The above pics were my first stab at this. was terrible!!!! Here is a couple pics as it...
Hi Bearuno,

Agree 100% on the motor placement. The above pics were my first stab at this. was terrible!!!!

Here is a couple pics as it is today.

Hi Alan,
What clutch cable did you use on your bike, the stocker appears to be 2" too short.
Mark

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