Yamaha TRX850 Enthusiasts Forum

Just sent a head to one of the more insane tuners in Sweden and he made some comments on it....
He thought that it was the best head he seen in original state and that yamaha really was ahead of time when making it.....mostly due to it´s intake ports.
Exhaust ports should have been bigger though.


....this was ONLY for those interested....

so will you be making the inlets smaller as per motoman

steve speed wrote:so will you be making the inlets smaller as per motoman

Absolutely, but not in the same way.
And the carbs will end up ~45mm also ported for best flow...not drilled as a lot of quad tuners do....we´ll see what we can do about the exhaust....

what's your aim, top end only, or?

HansJ wrote:what's your aim, top end only, or?

No, still rideable in the mids....BUT...we will see what the tornados do....can´t see how they would contribute to more top end than kent though. Same idea only open longer and higher...

how did it go with the big bore was it worth it

cheesie wrote:how did it go with the big bore was it worth it

Of cource not!!!
....but damn the bike is fun now!!
Dyno time next friday....if i dare....4 valves is out of spec

...just don´t want to shim it now as i´ve got tornado cams coming in next week or so...
Will keep you posted!

Killerwhale wrote:Just sent a head to one of the more insane tuners in Sweden and he made some comments on it....
He thought that it was the best head he seen in original state and that yamaha really was ahead of time when making it.....mostly due to it´s intake ports.
Exhaust ports should have been bigger though.


....this was ONLY for those interested....

Also learned that Yamaha has made splendid arcs in the exhaust ports...but then instead of evacuate the gasflow goes downwards. Worth 2-5HP...must be welded up though...

So are you saying that big bore is a waste of time or just not worth the money?

will you be posting before and after dyno runs?

Will wait until everything is done to find out which is the best mod, and whether the porting was worth it

Pics of the exhaust porting when its done.

Dave E

slow codger wrote: So are you saying that big bore is a waste of time or just not worth the money?

will you be posting before and after dyno runs?

Will wait until everything is done to find out which is the best mod, and whether the porting was worth it

Pics of the exhaust porting when its done.

Dave E

Well, we who buy a TRX and mod it CAN´T be on a budget...otherwise we would go for a modern bike. So pushing in the kinda cash the bike cost in UK/Germany is quite insane.
Said that i think it´s funny to have a bike no one ever heard of with a tractor engine that actually pulls descent.....and the sound is....

If i would have added another third of the money spent i could have had a TRX turbo with 150-60 HP easy. But now i have more CC and can lower compression and add a turbo at will...

In short, go for a turbo for best bang/buck!
There´s a Swedish ER-6 with a small turbo on it, fast spool up but not that hot in top end.
They run it at 120-ish HP and it´s drivable as ´ell

sorry what I ment was worth it as in as good as the flatslides will you actualy feel a nice difference

cheesie wrote:sorry what I ment was worth it as in as good as the flatslides will you actualy feel a nice difference

Hell yeah, we´ll see what the dyno says but i expect a good bit of tourque. It pulls like never before (as it should)
BUT, as said...i got 4 valves out of spec but i´m pretty sure they where before as well so...

Also, i´m patient but when i was going to slide on the cylinders i got a total meltdown i was so pissed.
Cylinder hanged down on the rings and i showed ´em in with a screwdriver (it was either that or kill someone) so i guess compression could be better!