Thompson 240 Kit - Chain hits back tire......? Pics....


Bondo

Registered
#1
Morning, fellow Busa lovers.....

(Mods if this is in the wrong place, please move.....)

So I'm installing (or at least I was....) a Thompson's 4-8" 240 kit on my gen 2 Busa. All was going well until I got to the last step, installing the chain. Hopefully someone can help.

* Rear tire is all lined up and installed, but not torqued down, ready for the chain
* Front offset sprocket exposed to feed the chain thru
* I run the chain from sprocket to sprocket to determine length, remove a few links, and close it up.
* To my dismay, I observe that the chain, on the top and bottom, is TOUCHING the edge of the rear tire.


All seems to be installed properly, I can't tell what the problem is. Certainly its not meant to rub the tire, I'd have missing paint on my wheel by the time I got out of my sub-division. All equipment used was from Thompson's in the 240 kit I purchased. Nothing is binding anywhere else, and installation otherwise was a breeze.

Its an EK 530 chain and Vortex rear sprocket. It doesn't appear to be a wheel offset issue, it appears to be the distance between the rear sprocket and the wheel. Like it should be off to the left even 1/8 inch. But I didn't even install the sprocket; it was already on the wheel. I've dug again thru the boxes and found no missing anything. Thompson's was closed time I discovered this last night and I can't contact them until Monday. :banghead:

And the other thing is that if there IS a missing spacer that bumps the sprocket out a tad away from the wheel, it seems it would run the chain at a slight angle, and that can't be good.


Anyone have any experience with this?


Thanks for your input.



Here's a few pics of what I mean:


Rub:

2013-04-05204720_zpse6121d96.jpg


2013-04-05204814_zps122a2659.jpg



Hub piece in the sprocket seems to have a bit of room on it for a spacer, but is that right?

2013-04-05203314_zps3e690040.jpg
 

Fastfrog007

Donating Member
Registered
#3
Are you chain adjusters set equally? Maybe the wheel is crooked a bit? That's all I can think of, the chain on my ATC 240 was close, not rubbing tho. Pics of the offset front srpocket and the rear hub might help a bit
 

Bondo

Registered
#4
Thanks for the reply, Rooster. Yea, They're dead even, wheel straight. When I get home I'll snap a cpl more pics....
 
#5
I am just taking a shot here. Is the tire inflated to recommended pressure which would give it height and less width? Just a thought.
 

Fastfrog007

Donating Member
Registered
#6
Torque down that rear wheel and see what that does. I recall my 240 arm moving a visible amount when torqued down. Check the specs on the torque too, it may not be the same as factory. Not sure if that'll fix her up, but its one thing to eliminate.
 
#9
i dont think people use front offset sprockets on gen2 240 kits, move the spacer from the front sprocket. stock the spacer is in the outside of the sprocket move it to the inside it will bring it out a tap i seen it done it works. hope that works.
 

Professor

Hayabusa Immortal
Staff member
Administrator
Registered
#10
I'm not familiar with the Gen II installs. But the concept is the same, was the teeth on the countershaft sprocket moved outboard per the kit specs. Was 1/4" on the gen I bikes.
 

Bondo

Registered
#12
Thanks, all. the front sprocket is offset .25".

@ Runner - the tire is inflated right, if anything its over a couple lbs.


@1bondoman 300's have jackshafts - should be no reason for that- what brand of kit/bike was that? Just curious...


Think I'm gonna cut the chain to proper length and slip the master link thru and yank this thing tight and see what it looks like. I was expecting it to have a tad more clearance. Depending on how I hold the chain, it clears by like 2 index cards thickness. I didn't expect it to be a big clearance but at this point .25" would be welcomed. Guess I never had to consider the horizontal movement of the chain. Slight but this damn-near-touching and touching thing even a tinge of horizontal is tooo much...
 

Bondo

Registered
#13
Yep, right-sized the chain, slipped the link thru and tightened it out to proper tension, lined up axle and it is still touching tire. Methinks I might have to grind the inside of the frame before it will space correctly. I know I have to do that, so maybe I'll try it next. Didn't think that would be the cause. Will update.
 
#14
I've had same issue on our 929 with Trac 240, was too close for my liking. I made shims for front sprocket even though its offset sprocket, then used same thickness washers between rear sprocket & hub. I gained about 1/6 inch more clearance and all lines up. Been this way for 4 years & 30k.
 

Bondo

Registered
#18
@ jduran - I don't remember offhand, it came with the kit from Thompson's. Its a 17t .25 offset. I'd have to go look at the package in the morn...

@ andrew - what did you use to make the shims for the front sprocket? Or did you machine it? And how much thicker than the .25" offset was it? And did you use washers to bump out the rear sprocket?


And the $64,000 question.... how much should I be grinding out of the frame? I knew I'd have to do a bit but this sounds as though its gonna be quite a bit. My concern (of course) is frame integrity.


Anyone have pics of this? (I'm gonna go search for some too lol)


@ Rooster - I was planning on using a carbide burr on my dremel- Will the dremel not have enough juice to make the cut?




:alcoholic:Don't mean to sound like a dunce here-- I'm actually good with stuff like this, just never done this project before. Thanks for all the input, pplz. Much appreciated.
 

Fastfrog007

Donating Member
Registered
#19
@ jduran - I don't remember offhand, it came with the kit from Thompson's. Its a 17t .25 offset. I'd have to go look at the package in the morn...

@ andrew - what did you use to make the shims for the front sprocket? Or did you machine it? And how much thicker than the .25" offset was it? And did you use washers to bump out the rear sprocket?


And the $64,000 question.... how much should I be grinding out of the frame? I knew I'd have to do a bit but this sounds as though its gonna be quite a bit. My concern (of course) is frame integrity.


Anyone have pics of this? (I'm gonna go search for some too lol)


@ Rooster - I was planning on using a carbide burr on my dremel- Will the dremel not have enough juice to make the cut?




:alcoholic:Don't mean to sound like a dunce here-- I'm actually good with stuff like this, just never done this project before. Thanks for all the input, pplz. Much appreciated.
I didnt try that combo, I used a mini air grinder to a compressor. As far as the depth, I went a bit deeper than needed with no frame intergrity issues 3yrs later (2 season with the 240, 1 on stock arm) The internal structure of the frame is honeycomb, if you start to break through, your a bit too deep but you havent hurt anything, just stay a bit shallower from then on. I also did the frame below the arm where the chain is heading toward the front sprocket. I also had to grind the 3 bolts down that hold the rearset to the frame. It wasnt much, but it did need attention. Pics in the next post, gotta switch to the smartphone to upload pics.
 

Fastfrog007

Donating Member
Registered
#20
Note these pics are with my stock arm and sprockets so just look at the frame and not its relationship to the chain. I went a bit higher than I needed to aswell, if I was to install another kit, I'd get it all on and ready to go then use a marker to note where the chain passes the frame and add a bit to the top and bottom of the marks to allow for suspension travel.
It's a pain to remove the arm again to grind, but its really hard to get in there with it on. Not tryin to Dunce ya, just tryin to save you the time and prevent some errors I made when I went at this with no advice. Post up with anymore questions. :thumbsup:

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