crank seals nitrile or viton

[jonny500]

i have somhow been roped in to building 4 moped engines. i am on a tight budet as most of us are. i have been looking at crank seal and have found a general engineering bearing  and seal supplier. they offer 2 types of seal. the first and cheapest is are nitrile (black) for temperatures up to 120 deg c (248 deg f). the other type are viton (red/brown) for temperatures up to 232 deg c (450 deg f). i am unsure what temerture a 50cc 2 stroke engine crank seal would reach. i believe not to high as the fresh fuel and air charge is constantly passing through and all the real hot stuff is at the top. any help will be greatly recieved
best regards
john

[jonny500]

i have order the cheap ones now. just waiting for someone to tell me i did the right thing lol. no seriously any input would be great no matter how small or trivial
thanks john

[Lawnmowerman]

For a stock engine the Nitrile is fine.
The Viton is for tuned engines that get hot and reach high rpm.
I did some moped dragracing over here in the Netherlands and used both the seals.
The Nitril is oke,but need to be replaced more often. The Viton is more durable because they don't get hard that quick.

[jonny500]

thanks for that lawnmower. these particular ones are for a stock engine that is going for sale. so all is good
thanks again
john

[Friar-Tuck]

John,
 I did find several pages that identify several properties of compounds and common uses.
This page is very similar to most.
http://www.gatewaytoairguns.com/library/Standard%20O-Ring%20Composite.htm
   
 I guess the question pretty much boils down to "How fast can you afford to go?"
  The nitril should be fine for your application in the engine.
    I was wondering who you were able to purchase your seals from and how well did the work out.
There are several suppliers I found while trying to do some research on the materials qualities.
   Tuck\o/

[jonny500]

http://simplybearings.co.uk/shop/ thats the suplier by using them i manged to reduce the price of the same 2 x bearing and 2 x seals by around 50 - 60%. although they dont do every bearing and seal size i can usualy find most of what i need. thay also do discount for bulk orders with the first price break at 10. food for thought considering alot of guys on here are buy the same stuff. take a look at the site i think they have outlets all over the world. thanks for the info and taking the time to reply to my post. im am going to run a set of the nitrile seals in one of our engines to see how they hold up and go from there if they work the savings will be massive over time. thanks again tucko
john

[Friar-Tuck]

 Thanks for posting the info John,
   There are more guys showing up all the time from your part of the world so I'm sure they'll be able to benefit from your research and posts.  I'll snoop around for some venders  here in our neck of the woods...
 
  There is a company that micro polishes and coats bearing & Gears.  unfortunately they want like $650.00 to do an engine (Tranny & crank)     http://twostrokemotocross.com/2010/06/microblue-racing-sponsors-project-two-50-results-in-low-emission-yz250-two-stroke/
   
 It would be interesting to see how much difference there would be in a bike that went the whole "Mary -Ann" (ceramic,bearings,exhaust etc.)
   & a stock engine.
  Maybe when I win the Lotto I can have a few built and send you guys some for "Testing"...
  Cheers,
  Tuck \o/

[crazyolbastard]

Wow Tuck,   did you see the size of the worlds biggest two stroke?

Unreal.

It`s a must see.