YZ400for enduro's

hi guys

first time to the forum but seems a good find

im after some advice please. i recently brought a 98 yz400 with a view to race enduro's , and would be gratefull of any tips on bike prep,,,,its stock at present but im looking at exhuast option, maybe a white bros system, also id be interested in advice on flywheel wieghts /size etc. and anything else that may help a very novice rider

Thanks Guys

Welcome to the wonderful world of Thumpertalk!!!!!

Some of my friends that are into Enduro (riding the WR) uses the stock YZ 426 pipe and silencer.

They just purchase our used pipes.....

I sold mine to a WR gay for a couple of days ago.

Hope this helps.

I bought a 99 used with a 8oz on it, worked good the thing i found most helpful was uping the idle which cut alot of my stalling out. This winter i got a 51 rear tooth and put on a 10oz weight, but haven't rode it yet. I have stock exhaust with some jetting changes which I got off of www.strokerspeed.com in the questions area.



I converted my '99 yz for enduros with the following: Stroker exhaust with spark arrestor(Need SA for east coast U.S.), FMF power bomb header, main and pilot jet up one from stock with DVP needle ( I ride at 0-2000ft.), 10 oz. fly wheel weight, drop counter sprocket to 13 for most enduros, seat foam from gutsracing (stock seat will cause severe monkey butt in an enduro), tail/headlight from Baja designs(cheapest ones because they are just for show: no lighting coil), trimmed bars to 28in. with bark busters, moose skid plate, and I am getting a Clarke tank. You can get by on stock tank for most enduros here (plenty of gas stops)but is a bit of a pain if you going for a long day of play biking. Bike is excellent in the tight stuff, gearing steals top end but in combination with the fly wheel weight makes the bike very luggable (no stalling) and good to enter in tractor pulls! Have fun, it is a great enduro bike.

Do you have a contact # or e-mail for the company where you got the seat foam?

wehay numpsy! what's this 'ago'& why did it only cost a couple of day's!

i do UK enduro mr sandracer uk. for the two-man enduro's your tank is fine but you'll need an IMS, Clarke or a TY Davis for anything over 30 mins. flywheel weight definately.

call gavin hockley at GH motorcycles of colchester. he races YZ's & comes first most weeks. he'll give you tons of advice & sell you some in return. hes in TMX news every week.


thanks guys

any idea on ideal flywheel wieght?

ive been ridding without one for a while yet still stall from time to time

are the 6 and 8 ounce ones to light?

Try www.gutsracing.com or 1-800-342-1272. I am 6"2" so I bought the tall seat foam and cover kit.

Assuming no problems with water pump etc. 2 things come to mind. First, check jetting in bike. If it is stock and you are riding around sea level it is likely on the lean side which will cause a bike to run hot. Another problem that I have experienced is riding for an extended period of time putting around at low speed or letting the bike sit and idle. Open it up let the rad. shrouds to their thing as well as circulating

coolant. You should notice that any over-flow will cease. Old dirty oil could play a small role in heat dissipation. I am sure others on forum have input. Good luck!

Some overheating tips, I ride in Arizona!

Use Redline WaterWetter and deionized water only unless you need freeze protection.

Strip the paint off the radiators, I used gasket remover, it won't hurt aluminum.

Make sure your radiator shrouds are not bent out, they funnel air through the radiators.

Drill many small holes in the radiator louvers to increase airflow at low speeds

Buy the WR overflow tank, it'll mount on the YZ easily.

Ride Faster :)

Just a thought on the boil over from my experience with my '00 YZ426. I thought my engine was overheating as well when I saw it dribbling coolant after riding for about 15 minutes. Well, it wasn't overheating. It was simply getting rid of excess coolant. I had just filled it to the very top. I have since discovered that the proper level is about 3/4 on an inch below that narrow opening just inside the radiator. Haven't had to add coolant in 7 months now. And F-Pilot is right on the money about the Waterwetter and deionized water. I use that and also added one of those "supercooler" heat sink pieces at the return line behind the left radiator.

Does Redline water wetter replace the use of coolant? If so, what ratio with deionized water? BTW, gotta luv the knowledge on this forum. Thanks.

I think about a cup of water-wetter should be enough.

However, the stock WR exhaust is to narrow for the engine to breathe.

Try replacing the pipe and see what happens.


anyone have trouble with there yz400's boiling,

it happend to me last weekend as i was pottering around the woods.

is there any thing i can do about this?

Thanks for the advice guys.

i love it here, often at my local dealers when i ask advice i get the impression the advice im being offered is the advice which will profit him most, so im really glad i found this place.

when i boilded the bike i was struggling round a tight deeply rutted woodland track which was horribly wet and slippy, so i assume the over heating had a lot to do with the lack of airflow, and rider with little skill :)

im gonna get some new rad louves and drill holes as suggested and order a wr coolent bottle. im already running water wetter and find this stuff works wonders,

i spose the easy answer is just to ride fast as hell through the slippy woods..........anyone know a good orthapeadic doctor???

Originally posted by sandracer-uk:

i spose the easy answer is just to ride fast as hell....

That works for me.

I check my coolant before every ride and fill to about an inch below the cap, sometimes it lacks a little. Some guys run stiffer (higher release pressure) rad caps, I think a KX is like a 1.4, YZ a 1.1 (US), but increasing the load on all the hoses and seals like that makes me nervous (but my rads always get good air flow :) ).

What Boit says is true, if I top mine off it just spits it back out as soon as it is warmed up and water has expanded. I only use distilled water, I’ve seen the water jackets on my pickup and I don’t want the inside of my bike ever looking like that (my truck must be jealous).

I think the manual calls for 50/50 water/coolant, I increased the ratio of water to like 70/30 and my bike ran noticeably cooler, antifreeze isn’t nearly as efficient at transferring heat as water. I’m not sure why they want so much antifreeze in there, maybe to prolong seal life? My seals outlasted the impeller shaft which grooved and began leaking just a few months ago.

I just bought some Water Wetter too, I’ve heard it is better than antifreeze (unless you are worried about the freeze part).

ok today i just ordered the following;

-white bros exhuast

-WR coolent bottle

-hydrualic clutch

-49 rear sproc [have been using a 48]

-new grippy seat

-new tyres [ boy am i gonna be broke ]

ooooh and just entered my first enduro on the 25feb

i wanna order a flywheel wieght but the size issue still confusses me, i just dont want to lose the rip the bike has and i hear so many differant opinions on the best size,

ranging from 12oz to 6oz

anyone ridden a number of differant wieghts?

I had a 10 oz on my 98, off road I loved it, was a bit much for moto. I have an 8 oz on my '00 426, could use 6 oz for moto but the 8 oz works good off road. I wouldnt go any more than 8 unless you ride in greasey mud and rocks. Get a 51t rear and the bike will pull better in the nasty stuff.

Oh yea, a few ounces of WaterWetter will do just fine.

[This message has been edited by F-Pilot (edited 01-11-2001).]

Hey Sandracer,

What brand of clutch did You get?

If it was Magura, make sure that You get the new type with aluminium end cap on the slave cylinder and not the old plastic sh-t.

And do not "test" the clutch before it is fully mounted on Your bike.....


I ordered a Magura unit, dont know whether its aluminium or plastic on the end,,, ill wait and see.

gosh just taken the plunge and ordered a 10oz flywheel wieght to,

just hope i aint overtaming the beast.

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