Carb advice

Trying to get a '85 250wr to run clean. Water cooled, last of the twin shocks. Issues are, sometimes hard to start, Kickback on lever 30% of time, abrupt stop of lever 1/2 way thru 10% of time, Bad bog in initial 1/4 of throttle, then bike takes off like a rocket ! also leaves an exhaust trail like a rocket. Air filter ok but sealing flange starting to go bad, have one on order. filter to carb boot is good, carb to reed manifold is good, reeds are good. Lots of spooge coming out pipe, cleaned packing out twice. New petcock, float bowl set right, new float needle & seat. Mikuni 38mm- innards as received- main 410- pilot 35- needle 6dh20- needle seat 166 p8- slide 2.5- float needle seat 3.3. - needle clip 4 down. Appreciate any carb jetting or ignition timming advice, This one's giving me fits, Kicking leg starts to hurt just looking at it .

Pretty sure the crankshaft to gearbox seal is leaking. In addition to your batman smoke screen this would allow excess air into the combustion chamber creating pre-ignition (kickback) and gearbox oil would affect the plug making starting difficult.

A leak down test would confirm the integrity or none thereof, crankcase seals and gaskets.

I second that!! all my left kickers, have had or are in need of crank shaft seals on the transmission side. They would be hard to start cold, smoke, run ok at low rpm's , no real hit on the band and wouldn't rev out on the top. Also check your ignition timing on the kickback just to be sure. Does it ever run backwards?

Have had cases apart twice by a good engine builder. Bike bogs really bad at low rpm, then revs out to the moon, never had it go in reverse, only had that happen once on an OSSA.

Assuming that your crank seals are OK, I'd cut the slide to a 3.0, use a 40 or even 45 pilot, and put the needle clip on #3.

need to check timing and verify it is stock spec or retarded a tad..any liquid husky, especially a 250 should never kickback like that. apart from it being incorrect, it will ruin the sidecase, kicker parts, and possibly even the left case half or your foot.

I agree all the above. If a 250 is kicking back you have your timing set too far advanced, and it also sounds like you have an air leak somewhere, and possibly a leaking wet side crank seal.

Not only the crankseals. Also check cylinder base gasket,intake rubber manifold dry rot, and it's mounting gasket. Those are the possible leaks that would turn up an airleak. I have had to replace the intake manifolds on the large reed cage on my 84 250WR and 85 400WRX.

Had engine checked 2nd time around for seal leaks, all intake manifolds are good . Found timing too advanced, ( have '85 tech. spec sheet from original owner) that states - ignition advance on piston before TDC at 2.55mm, advance on flywheel before TDC at 20.3mm, had it backed 0ff slightly from the 2.5mm mark. Pulled plug, came out very wet, at which time took carb apart & checked all passages, now waiting on air filter element to come, old one had sealing flange starting to disintegrate. Do those timing settings sound right ?

how are you checking timing? degree wheel on crank on dial indicator using btdc at piston? i like the micrometer method, but others have used the wheel with success.

Heres a service bulletin that will confirm your timing. By the way the flywheel advance is measures in degrees not mm. For whatever its worth subsequent service bulletins I have show the 85 250 XC to have the same timing but the 250CR to be .61mm BTDC on the piston and 10 degrees on the flywheel.

The attached service bulletin also has the factory carb jet sizes. This will provide you with a baseline to check your jet sizes against.

If your carb jetting is at or near factory then this comment of yours leaves me to believe you are pulling gearbox oil through the left hand crank seal. It may help for you to share how you checked for seal leaks.

I agree, in his first post he describes the excessive smoke also. A leaking clutch side main seal can also pull air causing his lean condition. His description of the bike's symptoms is classic air leak.

I forgot to mention that based on the tech specs your Husky model has a compression ratio of 15:1 which makes kickback more likely when air leaks, incorrect ignition timing, and/or incorrect jetting exist compared to a big bore with say 8:1 compression.

Appreciate all your help & advice, timing was done with a dial indicator using BTDC at piston, service bulletin is identical to one that came with bike from previous owner. Only jetting differences from that are main jet 410 instead of 420, & needle seat as 166-p8 instead of R-2. Anybody know about the 166-p8 ? Received new air filter today , made a new gasket at carb to reed junction. Did not see a leak there but old one was questionable. will fit all back together and see what happens. After found that timing was way too advanced it was slightly backed off the 2.55mm on spec sheet.

Would it not be easier to do a leak down test to check for leaks ?
If you have had a shop pull it apart twice, did they check the left crank stub for wear where the oil seal sits. I have always been surprised how a piece of rubber can wear a hardened steel shaft

sounds like your timing is good to go with for now..but that is a huge jump in size for needle jet...you dont want to do that.

You need to verify that timing spec. My Racing Handbook for 1986 has the timing specs at .49mm BTDC ignition advance on piston for a 250.
2.05mm BTDC for a 400cc motor and 2.4mm for a 430ae and 2.64mm for a 500cc motor

I don't know about that needle jet, it is what was in bike instead of the R-2 on tech. data sheet. What do you recommend ? also on same sheet timing is stated to be 2.55 BTDC on piston. When found it was advanced to over 3.5mm it was set back to spec sheet # slightly backed off. I raised needle to middle position & put all back together. Started on 4th kick, slight kickback on 2nd try. Wants to bog at up initial throttle opening then kicks in quick to the point of lifting the front end & I ride way upfront. Anybody have a cure for the initial bog ? Other than that , seems to be running cleaner. Haven't done a leak down , but spray around with starter fluid shows no sign of leak. Would that way advanced timing cause a fuel build-up in crank ?

No, i'd say you still have carb issues, and maybe a crank seal. With 2 strokes, any air leaks can cause all sorts of dramas. Have you done a leak down test?
Tony.

I agree. He has an air leak somewhere and that needs to be found first.