Another little trick for the 900

sno_mo_racer · Nov 8, 2010

Well I tried some shimming up to a couple thick washers and didn't work so figured the blue valve spring wouldn't do. My buddy has an extra XC 500 engine so checked the spring on there and it worked out great. It is a pink/yellow spring part # 7041786-11. Think the new style springs are too small for this mod. need to go to the old style springs which are longer and stiffer. Haven't tried any other color springs in that style as the pink/yellow was all I have available but it seems pretty close. if someone has access to other colors and doing this mod then they might be able to find the right spring but this one feels pretty close or the right one. Not sure though as it is the only one I've tested.

sw · Nov 9, 2010

Any confirmation specifically for the seal/bushing in the valve body? Part numbers, photo's....thanks guys!

cgsleds · Nov 9, 2010

do you need to do this to a 06 900 or just the 05

BIGGDAWG · Nov 9, 2010

cgsled said:
do you need to do this to a 06 900 or just the 05

this isn't a have to do thing just something that has worked for people and it is on both 05 and 06

cgsleds · Nov 10, 2010

is it worth doing will i notice a difference on it

Danbot · Nov 10, 2010

cgsled said:
is it worth doing will i notice a difference on it

As stated in the 1rst post... there may be situations where the exhaust valves do not stay fully open at wide open throttle, this mod should fix that issue.
Let the few of us who have already drilled get some ride time in and we'll let you know!

cgsleds · Nov 10, 2010

ok thank you and i will keep watching to see what you all think

BIGGDAWG · Nov 11, 2010

Well the seals i ordered finally came in. they weren't perfect but with a little modding like everything else on this sled the look like the will work.

the thinnest seal i could find was .25 inch and they were too thick so i put them in the valve and used my 3" roloc with a sanding disc on it and sanded them down flush. they also seemed to drag too much. these are a double lip seal so i cut the big lip part of the seal with the spring off and they worked much better. you have to pay attention when installing the shaft through the seal and gently push the lip of the seal back down because it rolls up when you first install it and you can tell because the valve drags a lot on the seal.

sno_mo_racer · Nov 12, 2010

I forgot to measure the diameter of the exhaust valve stem. I know the outside diameter is 1" or 25mm. I wonder if the inside diameter is 10mm or 12mm? If so I found a seal here http://pdf.directindustry.com/pdf/gfd-gesellschaft-fur-dichtungstechnik-mbh/radial-lip-seals-with-ptfe-sealing-lip/61484-95617-_5.html which is 10mm x 25mm x 7mm and another that is 12mm x 25mm x 7mm.

BIGGDAWG · Nov 12, 2010

sno_mo_racer said:
I forgot to measure the diameter of the exhaust valve stem. I know the outside diameter is 1" or 25mm. I wonder if the inside diameter is 10mm or 12mm? If so I found a seal here http://pdf.directindustry.com/pdf/gfd-gesellschaft-fur-dichtungstechnik-mbh/radial-lip-seals-with-ptfe-sealing-lip/61484-95617-_5.html which is 10mm x 25mm x 7mm and another that is 12mm x 25mm x 7mm.

the shaft is .5 inch outside on seal is 1.25"

sno_mo_racer · Nov 14, 2010

BIGGDAWG said:
the shaft is .5 inch outside on seal is 1.25"

Right, when I got back from the garage for some reason it was 1.25" and I been putting 1" in post # 35.

Last year fall time when My father in-law overheated my engine I did a whole gasket change and didn't do a crankcase seal change. So I checked those seals and the magneto side crakcase seal fits the inner diameter perfect and just got to cut the outside one a bit. So it is Part # 18 on the pic attached. Now I got to order another. Or I will do an actual measurement when the caliper shows up to the shop tomorrow hopefully and get an acurate measure and might find one in the link posted above. Think the 15mm x 30mm x 7mm might be the perfect fit.

sno_mo_racer · Nov 16, 2010

BIGGDAWG said:
the shaft is .5 inch outside on seal is 1.25"

Sorry BIGGDAWG some how I missed this post. And metric for this I measured with the caliper 14mm x 31mm(I.D X O.D.).

I was searching ebay and found this http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280362222411&ssPageName=STRK:MEWNX:IT#shId for those who ebay and don't mind waiting since it is way out in Check Republic. LOL I completed the purchase and didn't realize where it was. But found what I needed so don't mind the wait.

BIGGDAWG · Nov 16, 2010

yeh i knew the metric too, will be trying ours out next week so will give a report

RMKrick · Nov 16, 2010

Come on guys get out on that snow. I want to know drill or just plug. Do you need a new spring if you just pull the hose?

BIGGDAWG · Nov 16, 2010

RMKrick said:
Come on guys get out on that snow. I want to know drill or just plug. Do you need a new spring if you just pull the hose?

patience grasshopper :face-icon-small-hap

heading to laramie next week will give a report when we get back from a 900 and a 975.

and no you don't need to change springs you can just plug yours and see how it works for you.

Danbot · Nov 27, 2010

Finally got out for some test 'n' tune today.
I was watching / listening for differences in how the exhaust valves work after doing part of this mod. If you guys remember, I didn't install a seal. I just drilled out the pressure holes. I can't say I noticed any difference from before. Perhaps it's only in certain situations that the valves have trouble staying fully open at WOT.
I was slightly concerned about the valves opening too soon, creating a low - mid bog, but it was just fine.

RMKrick · Dec 22, 2010

BIGGDAWG · Jan 6, 2011

to the top

jsledder · Jan 8, 2011

BIGGDAWG said:
patience grasshopper :face-icon-small-hap

heading to laramie next week will give a report when we get back from a 900 and a 975.

and no you don't need to change springs you can just plug yours and see how it works for you.

Umm.... It's past "next week" :lol:

I'm going to try the plug method first. I can't tell you how nice it is to have all you testers out there playing with things and sharing your findings for the rest of us. Imagine how many dead 900's there would be.

ADHD · Jan 16, 2011

just trying to keep this post alive. Was also wondering if the o-ring thing was ever figured out,will it work or not.

Another little trick for the 900

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