1984 WR400 help

hi guys, my father bought this bike new in 1984. trying to get it running right. its not far off. i have got it running decent (starting, idling, and low speed), but just after it hits the power band, it flattens out and loses power.

carb is clean- there are no mixture screws, i believe?

using 93 octane fuel mixed at 45:1

i tested compression recently and it was well over 200. i want to say 230ish. maybe the head was shaved? not sure what these have stock.

i also noticed that the spark plug is a b8es, i found online it should be a b8egv. not sure if thats true or not, and if it makes a difference.

i havent ran it this year, so i will soon be putting in fresh fuel, fuel line, fuel filter, carb clean, check reeds, and new spark plug, and see if that makes a difference.....

but any help/advice is appreciated!

there is an air screw.. did the bike run right before? might be a spark deal [SEM?]

I would recommend a leak down test and check squish band width 230 psi seems very high and might be contributing to the flat top end.i would also pull the stator and check all the wires/magnets leave the stator/flywheel off while you do the leak down this will give you access to the seal.

do you know what jets/slide/needle you have in the carb? are they stock?
that needs verified first. write down whats in there.
good work doing a compression test, but i think theres a good possibility your gauge is off. the big bores are usually around 180-190 or so, 230 would be straight race fuel only. the 87-88 250 bikes are at 220-225 new but they are kind of a special thing.
the bike sounds lean on the top end

Thanks guys. Did some work last night before reading these posts.

Carb clean, new fuel line, reeds were mint. Intake side of piston still had horizontal lines.

Couldn't get going too fast because I was in a small yard and also need new rear drum 6 inch brake pads. Can't find any online. Any leads? Also need a headlight bulb and maybe a speedo as it looks like mine got vibrated to death.

I sprayed the cylinder base gasket and head gasket with starting fluid while the bike was idling in the idle did not change at all.

Also removed old fuel, added 93 45:1 with some octane booster

I will post pics soon

Main jet was a 400

skip the octane booster, not really needed or even effective if you are running 93. they will survive fine on that.
have you really looked for rear shoes? ebay has tons, halls husqvarna has them among many other parts, phil @ Husqvarna-parts.com
has lots for your bike, HVA Factory

when you say it flattens out on top, does it kind of feel like the brakes are being applied? like its cutting out? bogging? clutch slipping sensation? does it feel rich or lean to you?

i im thinking your brakes are EBC # 602 OR 3 YOU SHOULD ABLE TO GET THEM AT ANY SHOP THAT SELLS EBC AND THAT IS ALMOST ANY YOU WALK INTO [shit dang cap lock]

yeah, not sure if his are the wides or narrows

i have a video of it running but cant upload it....


anyways, i looked for brakes but didnt have a part number.... the brakes are 1 inch wide. are those the ebc 602's?


it flattens out as in once the power band kicks in, you know it wants to keep going, but it wont. i think it feels rich. it doesnt cut out if i hold the throttle, it just puts along.

oh yes, one more thing. the rubber exhaust mounts were broken a few years ago. i thought that mightve been part of the issue (leaking exhaust). i replaced them and they broke after 1 or 2 rides.

the exhaust also has 2 small dings but they are not major

Justin- the reason I did octane booster was bc the compression was so high. Like I said I recall it to be 230 but ill test again next time I work on the bike

bike looks to be in really nice shape!
your compression reading is odd, would be interesting to know whats up with that.

230 is way too high for a bike with no exhaust power valve, that bike should be in the 130-170 range.

130, 140 psi??? i always get close to 180 psi on a fresh swede top end..my 88 250 has no powervalve and is well over 200...220 with new piston and break in. the 87-88 250 has higher psi than any of the other swedes ive encountered. when my 84 250 got down to 150 it wanted 1 size leaner main to not four stroke. with a fresh top end it was back to 180psi

I am going off memory. I will compression test it asap. It's in NH so as soon as I can get there. I'd like to brake pads when I get there though, so I can throw them in as well as check compression.

Anybody know which set is correct? 6"x1" rear drums

will have to check in the garage and see what my parts boxes say...do your shoes have the stepped notch where they go around the round pin or are they just a round cut-out? one shoe is a bit wider here than the other... i believe thats the only difference. they are all the same diameter