Decided to upgrade my Orion Apollo 250 with a Honda XR250R engine

[Landsvw]

I’m liking that! When I did my Honda engine into a Suzuki frame I found I messed up on the front to rear sprocket alignment. Not the front to back, or side to side but the vertical. It messed with chain tensioning. When the rear suspension compressed, it put too much tension on the chain. And, on rebound, it made the chain super loose. It has something to do with centerline of both sprockets and the swingarm bolt. Just something to keep in mind as you proceed...

[Megadan]

Originally Posted by Landsvw

I’m liking that! When I did my Honda engine into a Suzuki frame I found I messed up on the front to rear sprocket alignment. Not the front to back, or side to side but the vertical. It messed with chain tensioning. When the rear suspension compressed, it put too much tension on the chain. And, on rebound, it made the chain super loose. It has something to do with centerline of both sprockets and the swingarm bolt. Just something to keep in mind as you proceed...

The TT250/Hawk are this way from the factory, though obviously not as extreme. In fact, the TT250 chain slack spec is specifically set with the suspension compressed where the chain is at its tightest point. It's all about the geometry of the swing arm arc in relation to the front sprocket position. On our bikes the rear axle moves away from the front sprocket during compression, reaches the furthest point of the arc, and then will start to move toward it a little bit during the last part of its travel, the chain tension is set with the axle at it's furthest distance.

[Landsvw]

Yeah, I didn’t realize it on my mock-up so had big issues with chain too tight on compression and too loose on rebound. Finally put a home made spring loaded tensioner on it and seems to work fine. But, if I did it again I’d spend a lot more time messing with the perfect placement so the tension was tightest right at sprockets and swing arm centerline bolt being perfectly in line. Then it would be loose above and below the centerline. It’s complicated and I wasn’t paying attention. Got towed home the first trip out because of broken chain...

Heck, evidently my mad skills are good enough for a Chinese bike factory.

Being towed by sister...

[Weldangrind]

Originally Posted by jeffrey

My old LIFAN GY5 200 came with that problem from the factory. Wen you adjust the chain to specs it got real tight wen the suspension compresed.

I have an old Lifan that has the same behaviour. It's actually an ideal setup; it's the specs that are wrong.

My method with an unknown bike is to support the bike on a stand under the motor with the rear wheel off the floor, and then remove the rear shock. With the chain tension backed off, I place a scissor jack under the rear wheel and raise it until the center of the countershaft sprocket, the swingarm pivot bolt and the center of the rear sprocket are in a straight line. At this point, the chain should have very little slack, without being guitar-string tight. I tighten the adjusters at that setting.

I then lower the rear wheel, reinstall the shock and place the bike on the floor. I note the amount of slack in the chain at rest and document it. If the slack is excessive at this point, I need to consider a spring-loaded tensioner. If it is not excessive, I call it a win.

[Chineeske]

Originally Posted by Weldangrind

My method with an unknown bike is to support the bike on a stand under the motor with the rear wheel off the floor, and then remove the rear shock. With the chain tension backed off, I place a scissor jack under the rear wheel and raise it until the center of the countershaft sprocket, the swingarm pivot bolt and the center of the rear sprocket are in a straight line. At this point, the chain should have very little slack, without being guitar-string tight. I tighten the adjusters at that setting.

I then lower the rear wheel, reinstall the shock and place the bike on the floor. I note the amount of slack in the chain at rest and document it. If the slack is excessive at this point, I need to consider a spring-loaded tensioner. If it is not excessive, I call it a win.

Exact the same way I do it, always have done it this way especially on my old dirtbikes.

[Chineeske]

Here a picture to show you guys why I need to lower the engine


Do you see it???

















When I mount the engine like this, the chain will slice through my shift lever axle as a chainsaw



Take a look at the original XR frame, the front sprocket lines up with the swingarm axle. Guess Mr. Honda didn't put the chainroller there without a reason....

[Chineeske]

Originally Posted by roundhouse

What a great thread. I am smiling looking at all the pics. then I frown because i have the mechanical skills of a purple headed sea slug..........THEY DON'T HAVE HANDS!

Well, I am just an office clerk (sales in the food industry) so no, I don't do this for a living... trial and error, trial and error did I wrote trail and error???

Nike's slogan is a fact; Just do it!

Everyone can be some kind of mechanic, it's just a matter of (sorry, but again TRIAL AND ERROR!

But for your compliments!

[Megadan]

Fabrication as a whole is trial and error. Experienced fabricators are just guys that have made lots of the errors already lol.

[Landsvw]

Not to belabor the point, but on both my XR600’s and my XR650L, the sprocket, swingarm pivot and rear sprocket centerline was with the suspensions compressed somewhat... I vaguely remember even using a ratcheting tiedown to compress it, then I’d adjust the chain. So, it was somewhat looser on compression and also on extension with the tightest spot in the middle somewhere.

[Landsvw]

Any updates???

[OneLeggedRider]

I put an XL 350 in my Suzuki 230 Quadsport and it was difficult to say the least. The valve cover was almost touching the frame above and I had to use a heat gun to mold the gas tank to make room for the head. The biggest pain was the exhaust, had to fab a new header to clear the frame in 2 places and still meet the muffler. But at the time the fastest 4 stroke quad was the Honda 250X and I could easily outrun them.

[Landsvw]

Here’s my nowhere as sweet attempt... I put an Honda XR100 into a TC90 frame...

[dpl096]

Originally Posted by OneLeggedRider

I put an XL 350 in my Suzuki 230 Quadsport and it was difficult to say the least. The valve cover was almost touching the frame above and I had to use a heat gun to mold the gas tank to make room for the head. The biggest pain was the exhaust, had to fab a new header to clear the frame in 2 places and still meet the muffler. But at the time the fastest 4 stroke quad was the Honda 250X and I could easily outrun them.

I remember when the 230s came out. They were hot machines.

[2LZ]

Nice way to play!
On the reverse of this project, I believe the older XR 200 motor should drop right in on those mount points. Member Fastdoc dropped a CB (OHC) Lifan motor right into his older XR200. Fit perfectly, as I recall.

[Weldangrind]

Originally Posted by 2LZ

Nice way to play!
On the reverse of this project, I believe the older XR 200 motor should drop right in on those mount points. Member Fastdoc dropped a CB (OHC) Lifan motor right into his older XR200. Fit perfectly, as I recall.

Doc did a nice job of that swap. In fact, there are only two years where a CB or CG will not fall into place on an XR200; 1984 and 1985. Those were the dark years with a dual OHC setup and they weren't as reliable.