Throttles too light?

David · Post by **David** » Wed Jun 29, 2005 7:02 pm

Wood and Iron Design (http://www.woodandirondesign.com.au) in Perth Make head gaskets for sherco and gas gas and I have one in my 270 gasgas. Quite Cheap actually. Andy (the WA sherco dealer) at yesmoto sells them (http://www.yesmoto.com.au) so it might be worth asking him.

Neo · Post by **Neo** » Wed Jun 29, 2005 7:29 pm

Thanks Gents for a your great responses.

Howard, I’ve already done the retarded ignition trick some time back but would it be OK to fit a second (or third!!?) head gasket?

David L, Yes I really would appreciate a photo (maybe uploaded to this topic) to show a machine shop. I’m going to try the head gasket trick first but the flywheel will definitely be my next port of call.

Although these “power smoothing” modifications are just what I need, I still believe I may have an issue with the throttle spring. It’s just so flipping light! Even GGG’s Rookie takes twice the effort to twist and it flicks back with a snap. But not my Sherco. [-X

Howard can the PHBL have a heavier spring or have you ever had a weak spring in Dellorto carbs before? Could this possibly have been a modification that Shane did?

Now on to the new SY250F. - It looks fantastic. And yes, I would use it to balance in the lounge room every night (but not watching Big Brother – yuk!). But I thought trials bikes are supposed to be simple and lite!! Two pistons, two sets of valves, two exhaust systems and a frame that looks like it’s been changed to accommodate that Yamaha MX engine. I can’t wait to find out what this baby weighs. If it’s <72Kg it would be the eighth wonder of the world. ^(=)^

BJ shoot me down and prove me wrong, as I’d love to buy one of these for myself for an Xmas present.

Howard – so that's where you’ve been these past few weeks – riding MX bikes. :roll:

You know this is bound to make you dab more often, next time you compete!!

Thanks for your help gents.

Best of balance.

Neo
PS. David, Thanks for the tip on Wood and Iron Design

Sherco H · Post by **Sherco H** » Thu Jun 30, 2005 1:04 pm

Neo,
How far did you * your timing??. Feel you should be able to control the power, by this mod alone. If this is not enough you should be looking at a 200.
The Scorpa 4T is the single cylinder motor, derived from the YZF . One cylinder ,double overhead cams, five valves, and one exhaust with a dual outlet muffler.

Neo · Post by **Neo** » Thu Jun 30, 2005 9:58 pm

Hi Howard,

If I remember right when I checked the timing the plate was close to being fully anti-clockwise. I kept turning the plate clock wise (mm by mm) and testing until most of the popping stopped (remember I wasn’t so keen on the popping). This left the plate at about half way travel. I’m really happy with the way the engine runs and I’ve noticed that it’s quieter than most trials bikes. Which suits me find when I'm riding where it isn’t strictly legal. :oops:

I’ve already considered the 200 (Sherco and Gas Gas) but unless I can find someone who wants to upgrade (in exchange for my I downgrade) it’s going to cost more than I can afford. There also doesn’t seem to be any advantages in weight or suspension, just a shorter swing arm. I know as perfectionist you wouldn’t like the idea of these kind of modification, but I want to do things that are revisable so I can go back to the norm when I feel I have enough Trials skill tucked under my belt.

You know, I rode a Montessa 315 last weekend. It was such a pleasure for me to ride. I got myself in a tight turn with the steering at full lock. Gave it a touch of throttle and a slip of clutch and she turned the corner as if someone was gently pushing the back wheel (no kick and no steering twitch at all). As you can gather, I was impressed (But again it’s out of my reach). And I saw only one negative, the clutch seemed heavier. Having said all this, there’s no doubt in my mind that the Sherco could beat the Montessa on many other tests with many other riders. Just at my skill level and my riding style the Monti seems to suit me better. As the new kid on the block I chose the Sherco because of it’s weight and it seem five times better than the Fantic Section I had.

Well on the Scorpa 4T, I have to eat humble pie now. I didn’t really look at those photos closely. I just guessed the engine type from the size of the block and two exhaust pies. What can I say, but, “I can’t wait to see it in the flesh”! :mrgreen:

Best of boulders.

Neo

r2wtrials · Post by **r2wtrials** » Fri Jul 22, 2005 5:21 am

rather than get too technical i would just go for the black throttle tube... the slower action gives you more control and you will learn to ride it smoother.

If you find the bike too much of a handfull perhaps you could do a swap with your barrel and piston etc with someone that has a 250 and wants a bit more oomph... I have just gone the other way with my pro.. swapped my top end for a 300 from a 250 and it is great.... more the better for me!!

Perhaps you may be able to talk to Andy at yes moto to see if you can do a deal with a new top end... say Heath sent you and give maximum discount!!! :lol:

Neo · Post by **Neo** » Fri Jul 22, 2005 5:44 am

Hi r2wtrials

This situation is a bit better now.

I already have the black tube.
I discovered that the throttle cable was not sitting into the Carbie tube properly.
I had the Carbie needle clip in the wrong position
I gave the carbie spring a bit of a re-tension. – now the twist grip snaps back.
But best of all, I’m running the bike on 92 Unleaded. And the bike is OK with this because I previously retarded the ignition.

Going to do a bit more testing on the rock this weekend but if I’m still not happy then I might consider an extra one or two gaskets at the base of the barrel to lower the compression (as the Sherco has no head gaskets). Do you reckon this would be OK?

Best of balance.

Neo

r2wtrials · Post by **r2wtrials** » Sat Jul 23, 2005 5:42 am

Base gaskets are an option... just wondered if anyone does the head spacers like you can get for the gasgas'. Although not a fan of this method i have seen quite a few guys running these here.

Post by **David Lahey** » Sat Jul 23, 2005 6:07 pm

It is usually physically possible to fit thicker cylinder base gaskets to two strokes but be aware that you will be not only reducing the compression ratio but also changing the port timing. On a crankcase reed induction motor like the Sherco the height of the top edge of the piston controls the timing of the opening and closing of the exhaust and transfer ports. The difference in port timing made by fitting two base gaskets (1.0mm thickness instead of 0.5mm) instead of one will probably not make much of a noticable change to the way the motor runs but I mention it to explain why it is better if possible to fit a thicker head gasket if possible (changing the head gasket changes the compression ratio without affecting the port timing).
Another much much more expensive option is to have the inside of the head machined by a two stroke tuning specialist to reduce the compression ratio.

Neo wrote:Going to do a bit more testing on the rock this weekend but if I’m still not happy then I might consider an extra one or two gaskets at the base of the barrel to lower the compression (as the Sherco has no head gaskets). Do you reckon this would be OK?

Best of balance.

Neo

Neo · Post by **Neo** » Mon Aug 22, 2005 9:23 pm

Hi All,

I’ve tried so many things now but I’m still not completely happy with two things on this 02 Sherco 290 of mine.

1. Although greatly improved I’m still finding it hard to control the low down power. It’s not that there’s too much, it just that there’s still too much too quickly with too little twist of the throttle (black tube). In normal circumstances the Sherco is controllable. But it’s at times like Steep climbs and steep drop-off’s. Controlling that millimetre of twist is just too flipping hard.

2. Rear Shock is a bit too sluggish. With my weight (57Kgs) I think I need something with a bit less dampening to give me easier hops and softer landings.

To address point one I’m going have a go at fitting a couple of extra gaskets to the base of the cylinder (as the Sherco has no head gasket). David Lahey has rightly pointed out that this will alter the port timing. But can anyone think of any other effects this might have? And what else I might need to change to accommodate this modification. Eg. * ignition or change Carbie jets……etc. etc….

To address point two. - I’ve recently been told that the Olle Shock Absorbers can have their oil changed to a lighter weight. This worked great with forks, but does anyone know who could do this for me? I live north of Sydney so it would be great to find someone local. Or, has anyone heard of someone changing their Olle Shocker for something better or more adjustable?

I’d appreciate anyone’s help feedback or comments.

Best of balance.

Neo
PS – Howard, I was kind of hoping that this post might bring you back to Trials Australia, at least for a day or so!!!

David · Post by **David** » Mon Aug 22, 2005 10:46 pm

Hi Neo,
A solution to the acceleration problem is to buy a slow action throttle which can be purchased at trialzone (Don Murray) for $39 http://www.trialzone.com.au/accessories/parts_and_accessories/index.shtml

Throttles too light?

Head Gasket