Flywheel weights, two-stroke, etc?

[Trials Rider]

Hi All

Fly wheel weights have probably been mentioned before but I thought I would ask anyway, I have a DT230 which I love but it could do with a bit more low down torque, I have altered the power valve with surprisingly good results, this has lowered the top of the exhaust port.

Anyway I am looking at adding weight to the fly wheel and possibly to the back of the clutch basket, has anyone done this and if so what results?

Also for the two stroke techno people any other suggestions regarding electrical timing, carburation, reed valves and spacers would be appreciated.

One last thing, between the carb and reed valve there is a expansion chamber thingy on the top of the rubber boot, WTF is it and WTF does it do.

[Motu]

I thought the DT230 had plenty of low down punch,in fact a very experienced rider said he thought it had too much.The traction control was supposed to take the sting out of the bottom end and make it a bit more controllable.Adding weights would make it less liable to spin up down low...sounds like you want less low down torque? The chamber between carb and reed valve used to be called a boost bottle...I'm sure Yamaha has a more fancy name,but they were added for more low down response.The DT230 was a development of the DT200,to get a bike with more low down torque,

[Trials Rider]

Trouble I have is I am used to my Sherco trials bike where the engine just keeps rolling which makes life easy for plodding, if I could get a a bit more rolling in the DT engine would be nice, for tight creeks, rocks, logs etc, general torque from mid range up is fine, just the very low end is what I want to help stop stalling.

[marks]

I wonder if your DT is running right.

mine was (I sold it to my son) unstallable and had a great 'no spin but just keeps tractoring' bottom end which got me out of the pooh on numerous occasions


the perfect trail bike engine - in my humble opinion)

[Motu]

I found mine would bog out at low speed having to pull hard (soft sand as a good example) and needed a pop of the clutch with a bit of revs to get some wheelspin and control.More rider error there than bike error...think ahead and be more aggressive.That's the only time it's small capacity ever showed,otherwise it always punched above it's weight.

[Trials Rider]

Thanks for that, do you know what the YPVS chamber is between the carb and reed valves is and what it does?

[Woodman]

The technical name for the boost bottle was :" energy induction" . My old IT175j used to have one, pretty sure thats what it first came out on. Anyway its supposed to make throttle response better after overrun. I ran mine without it and couldn't tell the difference, and anyway who cares about throttle response on a 175cc 2 smoke.

[Trials Rider]

Shit the last time I saw your KLR650 I thought it was a 2 stroke , even after you tried to hide it in a deeeeeep puddle:facepalm:

[Woodman]

Shit the last time I saw your KLR650 I thought it was a 2 stroke , even after you tried to hide it in a deeeeeep puddle:facepalm:

Well it certainly smokes like one now.

[K slider]

I have put 13 oz on my YZ250 fly wheel its much better to trail and enduro ride and prevents it from stalling on tight turns and not so vicous. Ihave seen them at Ballards but any engineer could make you one and a long nut.

[Trials Rider]

Thanks for that, is 13 oz or 370 grams an average of weights used? did you have options of weights?

[NordieBoy]

One of the guys on ThumperTalk removed 629g off a DR650 flywheel.
Took a lot of work but was only just noticeable in use.

The '79-82 XR250 and 500 both had the same flywheel.
We lightened the XR250's flywheel and made it pick up through the revs more quickly but didn't lose any tractability or even tractorbility...

The good thing with flywheel weights is they are a completely reversible mod.

[Trials Rider]

Yes I must admit my DR650 is a gentle giant, very nice and forgiving to ride.

Also looking to put a split power valve split stream device that goes in between the carb and reed valves, would be interested if any has used one.

[K slider]

13 oz was quite extreme but the bike puts a load of HP

[Trials Rider]

Cool thanks for that, its all good info, starting to get a picture of what I need to do.

[Phreaky Phil]

I had a YZ250 that I used to race in Enduro's and hare scrambles. We put a Big (cant remember weight sorry) brass flywheel weight on it. It made it pull well down low and was much harder to stall. It would claw its way up hills and drop down to near idle without stalling. It was fast off the mark at MX aswell, it seemed to hook up better. I have riden an adventurised XR600 with a big flywheel also. It was like a tractor and smooth as a babys:moon: Mind you when you shut off the throttle that flywheel wants to keep on spinning, so the engine wont slow down as quickly. I guess your familiar with that riding trials bikes