trx 90 aftermarket swingarm questions!!

[69 goat]

I need some help with the build on my sons trx90/300ex sups.
I got a aftermarket swing arm and elka shock. off ebay!! swing arm looks like a KOQ but has flames made in the sides. it has a ear on top by the piviot bolt and i dont know if it needs a roller or some sort of chain tensioner. with all the travel the chain is to lose or two tight if you compress the susp.???

[LT80]

The 300's swingarm geometry isn't perfect.
Your too loose/too tight issue is the norm. :(

[jweidner]

Is it an actual 300 swing arm, I don't think I ever tried that. I have run the KOQ swing arm on a trx 90 (Square tube style) and had chain tension issues like you are having.

TRX 90 when adding travel will do this. Pivot point geometry in relation to counter sprocket and rear sprocket is off.

There are a couple other known chassis builders that have corrected this problem on the trx 90. I used them and they work.

I not a big fan of chain tensioners, that's just my opinion.

[LT80]

Sorry, I took it as you got a 300 swingarm.

[miniquaddad90]

I saw that swinger on ebay. Apeared to be a Fincher(profab) or some modded KOQ. Set your chain tension with your rider on it and you will be fine. We have ran a KOQ swinger for almost 5 years and have NEVER thrown a chain. However we do run a skid plate for XC racing on ours with a chain guide built into it. I usually leave about a 1/2" or so of total chain slack with the rider on it. This should get ya going!

The "ear" should be for a 400ex front chain slider along with 2 bolts that hold the slider on the side of the swinger.

[jweidner]

I ran an ATV Four Play rear swing arm most of last year and that seemed to work great. Chain alignment seems to be challenging for most chassis builder... at least for the trx 90 is concerned. KOQ, we used A spacer on the rear sprocket to get alignment correct. Four play alignment and tension was perfect with no spacer or tensioner.

You are right though.. check tension with rider on it and try to compress and make sure tension does not limit travel. Have seen too many little quads break chains due to these problems.

I normally will measure ride height with rider fully geared and then simulate that with rachet strap and then adjust chain.

....If your kid is like my nephew he has too much energy to just sit on a quad.