My Griffon Engine.

[greeves246]

my griffon engine

[dave higgins]

Hi gary, looks like your bike collection is stacked right up to the ceiling, 70 plus bikes need a lot of space, but going back to your griffon motor, can you see whether the crank seals can be replaced without splitting the crank cases.
I have not got time to break mine down, but changing the seals might help the lack of low end power when pulling away. dave

[Andy Z]

Hi gary, looks like your bike collection is stacked right up to the ceiling, 70 plus bikes need a lot of space, but going back to your griffon motor, can you see whether the crank seals can be replaced without splitting the crank cases.
I have not got time to break mine down, but changing the seals might help the lack of low end power when pulling away. dave

Hi Dave,

Yes, it is possible to replace them without splitting the cases.

Cheers,
Andrew
#190

[Kim275]

If you have never replaced them follow this. For the seal on the Sprocket side . seal is easily accessible once you remove sprocket. Just apply gentle heat to casing and you can get it out with a screw driver. Note which way round seal is ( open side facing you) . For putting in new seal again heat the casing and then coat seal in your 2stroke oil and tap into casing using old seal as a drift . Simples! Again coat sprocket with 2 stroke oil before refitting on shaft an making seal. For the seal on flywheel side.... Well have never actually replaced one!! Gary/ Andy any tricks to that one or is it straightforward? Cheers Kim

[riflegreen]

The drive side oil seal goes in with the closed side facing you , if open side facing you then crankcase pressure goes straight into the chaincase .

Timing side is easier still , pull off flywheel , two centre punch maks , one on the stator edge and the other on the mag back plate to retime the ignition , oik the seal out with a screwdriver , bit off oil on the seal and tap into place , closed side out .

Back in the day it took me three minutes to change the timing side seal , the drive side seal never wore out because of the lubrication from the chaincase oil , the timing side one needed every bit of help it could get .

Sure sign of the timing side seal going is if the bike wants to tick over on a fully shut throttle .

Lack of go from start is not down to seals.

Chris

[dave higgins]

Thanks for the input lads & i hear what you are saying riflegreen, but if you are drawing air through your crank seals, its going to run very weak & your never going to get it to a good state of tune.
I have got a problem with it & seal replacement was a process of illimination more than anything.
Its not some thing that i have really looked into to deeply at the moment as time is short & i have another ride, but i would to sort it soon.
The bike is very quick, it revs out cleanly, it idles smooth, it goes from idle to full throttle crisply, but pulling away, well its like using fourth gear, any ideas anyone.
Sorry to hijack your thread gary, but when i saw your engine with the cover off, it reminded me, thats all. dave

[greeves246]

Garys brew ! Lol

I HAVE A LETTER FROM DAVE HARPER SAYING SEALS, PISTON RINGS, AND NEEDLE, NEEDLE JET 330 MAIN AFTER RUNNING IN 300 I THINK HE SAID

APARENTLY THE NEEDLE WEARS THE NEEDLE JET OVAL ! WITH THE INDUCTION FORCE !

THE SEAL ON THE DRIVE SIDE CAN BE REMOVED USING A SMALL DRILL AND A SELF TAPPER ! GENTLY TO EXTRACT IT !


GARY

[156trials]

A lot of people are under the illusion that crank seals on 2T motors commonly fail, and need to be replaced. In actual fact what is far more common is that main bearing wear means its not possible for the seals to work properly.

[greeves246]

griffon engine

note the ports are square on the engine and the pipes round so there must be a gas definency there somewhere !

[dave higgins]

156 trials, whats your point, the end result is the same, splitting the crank to overhaul, but this tread is about garys 380 twinport motor.dave

[Brian Catt]

It's a bit like the Ferrari engine failure story....Ignition fault! Yes the con-rod took out the coils.

[156trials]

156 trials, whats your point, the end result is the same, splitting the crank to overhaul, but this tread is about garys 380 twinport motor.dave

Point is a lot of people seem to think changing the seals without new main bearings, will mean air leaks caused by main bearing wear will then stop. There is a vague possibility that nitrile seals would fail over a long period when using ethanol type fuels, but other than that seal failure is almost unheard of.

Heres an example: http://www.trialscentral.com/forums/...52#entry273652

[greeves246]

Gary

THE MAINS IN THE GRIFFON MOTOR IS BUILT REAL HEAVY ! OVER 1" DIAM AND WIDTH ( WOULD HAVE BEEN BETTER WITH REPLACEABLE BALL BEARING AND KEPT THE MOTOR NARROWER USING BIGGER DIAMTER GEARS IN THE GEAR BOX AND NARROWING THE WHOLE ENGINE AND BOX ! FOR DESIGN PURPOSES :-) BUT WE CANT GO BACK AND RE DESIGNE IT ;-)(THE SIDE BEARING WILL OUT LAST THE SEALS BUT THREE TIMES OVER) QUITE SAFELY BUT I THINK THE ETHANOL WILL BE A PROBLEM OF THE FUTURE AS THE GOVERMENT SEEM TO BE KEEN ON ADDING MORE AS TIME GOES ON

THE ORIGINAL SEALS WERE MADE BUY STEFFA I HAVE THEM, BIT TOUGH THOUGH !!!!!!!!!

[156trials]

The probable reason why your seals are failing so quickly is probably due to the effect of ethanol on nitrile rubber. Some dealers are sure to have lots of nitrile seals they are want to shift though, so they are unlikely to advise fitting them is going to cause problems. Wonder why you always post in CAPITAL letters?

[Grytpype-Thynne]

Wonder why you always post in CAPITAL letters?

His shift key's stuck. Or something.