Yamaha TRX850 Enthusiasts Forum

What do Kent cams / ported head feel like to ride on the ole seat of the pants dyno? Eg power characteristics

Pretty damn quick by the seat of my pants

Albeit with big valves and Fcr's, indecently quick and oodles of midrange grunt if you take the time and effort to dial the cams in spot on using slotted cam sprockets. I generally find myself short shifting and taking advantage of the abundant torque. Only really need to rev it to 8k at trackdays whilst chasing inline 4's down the straights.

This thread shows my dyno charts:

viewtopic.php?f=6&t=9626#p98380

Mark.

On their own (and assuming that you already have FCRs and a free flowing exhaust) - about 4 to 5 bhp if you are lucky. BUT, it should all be in the midrange so you should be able to feel it.

I'd recommend some dyno time to get the fuelling right

Cheers, just where you want it, did you have to adjust your can timing / use slotted sprockets?

You'll need to slot the sprockets to properly degree the cam in - especially if the head is skimmed

dandywarhol wrote:You'll need to slot the sprockets to properly degree the cam in - especially if the head is skimmed

I'd disagree - can you expand on that please?

NWS870R wrote:

dandywarhol wrote:You'll need to slot the sprockets to properly degree the cam in - especially if the head is skimmed

I'd disagree - can you expand on that please?

I like to have cams timing as close to spot on as possible and using a degree disc and slotting the holes if needed. Early years I even cut out crescents of alloy to fill the slots in case the cams slipped but that was overkill )

If the head has been skimmed then the cam timing will retard as the chain run from the crank to the cams hasn't altered but the cam sprockets are closer to the crank sprocket so slotting the sprockets will be essential for the cam timing to be advanced back til it's correct.

Spot on expalanation Dandy

Was just going to reply myself. Fortunately you posted just a few seconds before I started bashing away at the keyboard


Mark.

sanddune51 wrote:Spot on expalanation Dandy

Was just going to reply myself. Fortunately you posted just a few seconds before I started bashing away at the keyboard


Mark.

I than-queue......................

Alan

There is very little in it though - even with a couple of thou skimmed off the head - is as near as dammit though with standard (non slotted) sprockets.

A couple of thou barely cleans the head up - I'm talking of skimming a head 0.25/0.40 mm to raise the compression - then you need to slot the sprockets

As Phuk pointed out there is so little in it i can't see it's worthwhile, the Kent YAM9 re-profile is so mild that it certainly wouldn't warrant slotting the cam sprockets IMO. Had my head skimmed/flowed some 15 years ago & all is good without altering cam timing/slotting?

Horses for courses, or horses for little expense??

Sorry, i don't don't do riddles

I'm talking of skimming a head 0.25/0.40 mm to raise the compression - then you need to slot the sprockets

I hadn't thought of this ...good to know! Head-shave is coming up on my list in the next few weeks. How many cam degrees thereabouts would we be looking at?