I need a structural engineer.

Message

protraxrptr17 · #1 Post by **protraxrptr17** » Thu Jan 06, 2005 2:24 am

Is there a hard and fast rule about using the swingarm pivot bolt as an engine mount? My 525 came in today and the swingarm pivot/engine mount is way off. The 525 mount is much wider and much farther to the left than the 660. I can cut down the mount on the engine but I would really hate to do something that drastic. Cutting the left side of the swingarm down isn't an option. It's way too narrow. If I can just mount the engine a little farther forward I can also change the relationship of the front sprocket/pivot/rear sprocket to take advantage of engine torque's effect on suspension action. Maybe a threaded adjustment so I can change it for different conditions (patent pending, HAHA!) Anybody looked at Walsh's chassis to see what they did?

Doug did you get that far along on your conversion?

c41xracer · #2 Post by **c41xracer** » Thu Jan 06, 2005 9:35 am

i didnt use mine in my crf conversion and it didnt seem to do any harm.

cannondale27 · #3 Post by **cannondale27** » Thu Jan 06, 2005 12:42 pm

You dont have to use it but having the sprocket as close to the swingarm is important to minimize the torque effect of the chain on the suspension.You could use something like they offered for Banshees if you have to I believe it was calles a Amplink.

protraxrptr17 · #4 Post by **protraxrptr17** » Fri Jan 07, 2005 3:03 am

Yeah, that's a good idea. I think the countershaft is located much closer to the rear of the 525 than the 660. I didn't measure it before I sold it. I'm in the process of getting the distance between the swingarm pivot and center of the 660 countershaft. I posted it on romper room but I don't think playskool makes a functional tape measure.

haydug · #5 Post by **haydug** » Fri Jan 07, 2005 1:06 pm

I am using my bolt yes, on the custom frame, the swingarm and frame were made to the KTM engine, on the 400ex conversion, JB had to modify the swingarm on the left side to sit the engine over to align the sprockets. I know of another 400ex conversion where the owner milled some material off the case to get the engine over. I would try like **** to use it if I could.

c41xracer · #6 Post by **c41xracer** » Fri Jan 07, 2005 5:02 pm

i agree use the pivot bolt if you could......but i couldnt, i had a 250r chassis converted to fit a crf450

protraxrptr17 · #7 Post by **protraxrptr17** » Sat Jan 08, 2005 4:04 pm

Well, I'm going to use the pivot mount. The sprocket was just too far back. It's going to be tough because I have to get a custom swingarm with the left main beam angled to the left, I think it's going to be about 1 1/4 inch. I talked to RPM yesterday and he said he could send me all the pieces and I could cut them and weld them together like I needed them. I'm going to do a little more measuring today because a 250R swingarm fits the back of the engine and the chain lines up perfectly. Maybe he can build me a 250R swingarm without the linkage mount and I can weld it on myself. I just don't know how the rear tires would align with the front tires, because a Raptor is offset in the rear. It's going to be alot of work, but an 80 pound weight savings with a 25 horsepower gain is going to be worth it. Not to mention, being totally different from the crowd, and the satisfaction that I built most of the stuff myself.

protraxrptr17 · #8 Post by **protraxrptr17** » Sat Jan 08, 2005 9:21 pm

Just got off the phone with Joe at JRD. Man, that is the coolest chassis/suspension company I have ever dealt with. He said it would be no problem, just send him a Raptor swingarm to look at and he would build whatever I wanted. Plus he gave me a steal of a price too. I have to move the shock and linkage mounts on the frame anyway, so this is going to be the best way. The 250R swinger is exacly 2" longer than the Raptor which is what I wanted anyway. I gotta get Jeff to revalve my rear shock to work with the new length and weight.