XR 650L chain guide mod - Acerbis tank

I read somewhere that if you go to a 48 tooth rear sprocket you have to modify the lower chain guide to avoid premature wear of the chain guide. Haven't seen it on the posts. Anyone hear of this? Mine is a 2003, larger sprocket seems to clear the guide, but the chain sits lower of course.

Also my newly acquired bike has an aftermarket Acerbis 5 gal(?) tank. Nice to have the extra capacity, but the mounting systems doesn't inspire confidence (2 little straps up front, nothing holding it at the rear). With the LA-B-Vegas coming up I need to know this thing will stay put!

On the posts I see folks using IMS and Clark tanks, not Acerbis, is this why?

Anyone have experience with these tanks?


If you go to a 14-tooth front sprocket, that should be low enough gearing. I'm not one who likes having a larger diameter sprocket hanging out back there to get nailed by rocks. My gearing is stock.

Here are the chain guide modifications I did: (I've posted it before)

Rear Guide

Front Lower rubber thingy replacement

The Acerbis Tanks hug the frame too tight. It makes it so that air cannot get to the top section of the frame and cool the oil properly. Don't get one!! I have an Acerbis 6.0 gallon on my '95 650L. A week after I put that tank on, it started burning oil. It still burns oil.

I once considered installing an oil cooler a-la XR400, but have yet to get around to it. At over 55,000 miles, I don't think I will. :applause:

Here are the chain guide modifications I did: (I've posted it before)

Rear Guide

Front Lower rubber thingy replacement

I would like to get the same rollers.

Do you have the partnumbers for those?

Will I need any other mods to make them fit?

I have a 48 on and the guide wear looks 'normal'.

Hasn't sawn through it in 4000 miles, anyway.


I have an Acerbis tank and I think its the best thing I bought for my bike. I just put 4000 kms on it in the Baja (three crashes) and no problems. The mounting hardware for the front is two sturdy pipes with flattened ends and there is a frame mount in the rear. It sounds as if you have the wrong or missing mounting hardware.

Thanks for the reply. Acerbis sent me the mounting diagram. there is a cross tube with bungs in the end that mounts to the frame. The tank seems to slide over this and engage it. Problem is the metal tube vibrates against the inner panels of the tank and chews it up - the bungs are cheap thin plastic and don't offer much protection.

the flat metal tubes at the front look kind of flimsy but do seem strong when everything is tight.

I don't see any other mounting points in the diagram. I got the bike with the tank on it - I think it has been on for about 2,000 mi without obvious problems. Unless I am missing mounting pieces and you Baja tsted it it is probably OK. From what I can tell most aftermarket tanks just aren't up to OEM standards. Most people on the posts seem happy with them.



I am running a 14/48 on my L and havent seen any significant ware on the guides at all. One thing I have noticed is the lack of chain stretch on that stock honda chain. Not this relates but my bike came with an additional clark 4.3 tank and it does have a bolt mount on the rear near the seat.

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