350x/400ex transplant chain issue

[Rocks&roots]

ok here it goes,when I sit on my trike the chain gets looser,I installed a 400ex motor in my 1986 350x frame using the correct motor mounts and engine mounting positions,what would cause this ? I have one possibility or2 ,1st the rear shock dog bone is upside down? or is the front sprocket a bit higher than a stock 350x x ? its definitly a geometry issue but its bugin the hell out of me,I followed matt350x"s build thread and did notice the shock dogbone [link] does have a direction arrow but cant seem to see it on mine< anybody please chime in there has to be a solution!

[Red Rider]

Reading about your issue, I don't see how the shock dogbone could have anything to do with that. Regardless of which way the dogbone is positioned, the swingarm still has only one pivot point, and flipping the dogbone over will not change that pivot point. The way I see it, it has to be the height of the countershaft sprocket in relation to the swingarm pivot.

[Footy]

I cannot answer your question. I have a dirt bike that does the same thing.
Maybe you will need an idler sprocket on this setup or maybe a device like the old AMP link .

[ATC King]

How many chain drive, rear suspension vehicles have you owned?

Edit: That's not trying to be ugly, just that if you haven't owned many it may be a new thing to you, which is why I went into more detailed information.

There is always going to be tight and loose spots in the chain as the swingarm moves through its arc. That's why an owners manual specifies a certain amount of slack during adjustment, to compensate for the tightest point in travel.

If you've modified engine placement, at all, it's going to change that. You can remove the shock spring, set the trike up on anything that'll let the swingarm move through its full travel, and check the chain as you do that. Find the tightest spot, adjust that until there's no slack (but not piano string tight), then the slack it has while in the normal resting position, with the spring back on, will be close to ideal.

Some machines get tighter as the suspension compresses and others get looser. There is no solid rule, just the way they're designed. All that matters is the chain is adjusted so it's not overly tight when that point comes around.

You could always get a fat friend to lean on the thing while you look. Better still if you have one with enough mass to fully compress the suspension. I guess piling rocks on it would work to, but that's just too much work. Maybe a skinny friend and a backpack full of rocks? Either way.

The only way to have a chain that doesn't go through wild swings in tension as the suspension travels is to put the pivot inline with the output shaft. That is a very uncommon design, because it has it's own issues, and pretty much is something engineered from the ground up, not a modification that could be easily done.

Here's what that looks like.



Here's a few words about it.
https://www.motorcycle.com/features/...0x-review.html

Perhaps the single most impressive design element of the G450X is the exclusive implementation of a coaxial swingarm pivot/countershaft. A hollow countershaft serves as the swingarm pivot bolt hole, allowing the countershaft sprocket to rotate around the swingarm pivot point. This completely eliminates the need to adjust the chain to accommodate the wild variations in tension due to 12 inches of rear wheel travel. It’s a surprisingly simple solution to a problem that has been the bane of long-travel suspension since its introduction over 35 years ago. It’s ironic that BMW would be the first manufacturer (not counting start-up MotoCzysz) to implement this ingenious design.