1974 250 Mag Baseline 36mm Mikuni Jetting

[D-Dub]

I’ve looked through the threads and have not found any here. My bike has an older 36mm Mikuni conversion. I’m fighting a hard starting issue, bumps starts fine, and would like to verify that my jetting is good while I run the Motoplat tests.

Thanks,
Dennis

 

[D-Dub]

Anyone with a 36mm Mikuni on a 250 mag that would care to share their jetting specs?

 

[Vinskord]

This may help:

http://www.cafehusky.com/threads/250-mag-intake-question.44721/#post-436630

See #10

 

[Kartwheel68]

It is probably not the carburetor or the ignition, it is almost for sure that ridiculous kick lever. Husky did such a good job on the rest of the bike, it is beyond me how they put that abomination of a kick lever on their bikes.

 

[stormer254]

It is probably not the carburetor or the ignition, it is almost for sure that ridiculous kick lever. Husky did such a good job on the rest of the bike, it is beyond me how they put that abomination of a kick lever on their bikes.

Got to agree how such a good bike can have such a s**t kick start is almost unbelievable and the same basic design carried on till they went bust!

 

[Kartwheel68]

It was 77 with the 250/390 CR (I think, but for sure 78) that they changed the old lever to the much better "S" shaped lever they would use until the straight aluminum lever in 84. The 77(78)-83 lever is WAY better than the old style lever, and putting one on my 76 250WR is the best thing I have done to it.

 

[D-Dub]

Ok, I have a kickstarter off a 1980 CR250 that fits. It clears the footpeg unlike the straight stock one and I assume that few extra degrees of rotation at the bottom of the stroke will help. I'll try and start it tomorrow. My only concern is at full clockwise the lever will contact the clutch cover and there's some concern of breaking the cover.

 

[D-Dub]

All Motoplat tests per Vance Smith turned out fine so I believe the starter lever is the culprit. FYI here are my 36mm Mikuni VM specs:

Main 330
pilot 35
needle seat 3.3
slide 2.5
main tube 158 Q-6
needle 6DH2
float set at 18mm

 

[Kartwheel68]

Try a 40 or 45 pilot, 35 seems a little lean, but I dont have any specs for a 36mm so it could be correct.

 

[Jeff B]

I have a 1975 WR 250. (same basic bike) My starting procedure with the 36 Mikuni. Choke on. Don't touch the throttle as it is not really a choke, it is an enrichment circuit. Tilt the bike over til it spills gas all over your boots. Hold kill button down. kick it a couple of times without any throttle. You want to sort of flood it a little in cooler weather. Stand on a small stool to get better kick. Now kick the snot out of it. My WR will usually start on 2nd or 3rd kick cold. I'm sorry, I don't have my jets written down. BTW It may become easier to start when the weather warms up. Jeff

 

[D-Dub]

Thanks Jeff and all for the responses. I tried it yesterday using the method of rocking it in gear and it fired but did lite off. I’ll have to keep prodding it until I get a consistent result and I’ll certainly try your method.

 

[Crashaholic]

I used to ride a 73 450 and when the motor was tuned properly I had no problem starting that monster with its POS kickstart lever using my left leg. I agree the kickstart lever could have been improved but thats for another discussion. Point is, when tuned properly and parts are in good condition starting these bikes doesn't have to be a pain.

If you're sure there are no vacuum leaks, your ignition is producing a rich blue spark, and the motor is getting fuel or not flooding then I suggest retarding the ignition (moving closer to TDC) 1/2mm at a time up to 2mm to see if that helps.

I rebuilt a 75 360 a years ago and used a dial indicator to set the timing to factory specs, it turned out to be a pain to start. I retarded the timing a bit at a time until it fired up the first or second kick every time using my left leg. Doing this will reduce the max HP output as determined by the factory but probably only a small amount. You have to weigh the loss with the benefit.

Something else that comes to mind regarding the inadequate kick levers on these early bikes is to set the kick lever to engage the kicker mechanism as soon as possible. The only setup procedure I know of for this is to mess with the lever placement on the spline shaft until engagement is about a 1/2 inch off the rubber bumper. Be sure to check this when the bike is running to be sure its not starting its engagement any sooner or it could grind the teeth down on the kick starter gear. When the motor is running there will be a clicking noise at the point of contact between the starter gears as the lever is moved away from the bumper.

 

[D-Dub]

I’m at 18 degrees before TDC right now which is the factory spec. I’m experimenting with the kick engagement point as well.
Thanks, Dennis

 

[markt2]

Biggest problem is one kick stroke seems to barely turn the engine over 1 revolution... slowly bringing the engine up on compression, letting the kicker come back up to reset for full travel, and then giving it a good kick through helps a lot.

Careful with the kick engagement point... lots of covers have been broken by adjusting the starter to engage sooner than specified in the manual... 20mm to 30mm off the bumper. Works okay engaging sooner until that first kick back.

 

[DeathFromAbove]

I agree for sure about all the posts here, I respect all the posters, but i have found that it is all carburetor. The timing is finite. On or off.. I have a 1971 360c enduro that starts on the first kick most every time. I also have a 1983 500xc that takes some "prodding"! Both have new top ends, the 360 ran without a rebuild but was marginal, the 500 was seized. Both were rebuilt with new everything. The CARBS were rebuilt with the same parts, jets and all other parts. The 360 starts right away, the 500 needs some LEG work!! One day I will figure the 500 carb out They can be made to start on the 1,2 kick. We all are looking for the answer! Good Luck! Thanks Chris