CAN'T START RESTORED '74 250 MAG!!!

[metalhof]

Feel like an amateur here...but I finished up completely restoring a '74 250 mag a couple of weeks ago. Since then, I have not been able to start the darn thing. Have pretty much (maybe) pinpointed it down to being a bad Motoplat, but not sure and hate to shell out the bucks if not needed. I have pulled the carb several times and recleaned, everything is good there, has all stock jetting. Seems to be getting fuel but not much on the plug after kicking extensively. Seems to get fuel if I open the throttle and overflow the carb with the Tickler. If I pull the plug, I get spark, but just seems like it's intermittent, and only really good spark with a really hard kick, but not every time. Was told this is typical of the Motoplat, but just doesn't seem right. In checking what I can check on the ignition, Im getting 300 ohms from blue wire to ground, 16 ohms between black and blue wire, and 6000 ohms from plug wire to ground. This doesn't match the readings that i've seen on some websites, but not too far off. Ive got compression (new rebuild), spark (intermittent), and fuel....but, not even as much as a fire, or an attempt to fire. Even pulling plug and dropping some gas directly on top of the piston, I get not even an attempt to fire. I double Checked the timing and it is set at 2.5mm from TDC, which should be correct. Am I doing something wrong, or am I missing something?? Also, with using the tickler, should the bing carb just dump gas right out the overflow and out the bottom of the bowl onto the freshly painted motor??? Seems like a poor design. Any ideas? Im getting frustrated and don't know where to go with this. As it sits, it pretty to look at, but not much fun!!!

 

[halffast]

Try to bump start it . My Mag was a terrible starter until I went to an Mzb ignition and a Mikuni carb . With the Bing , if it didn't fire after the first 3 or 4 kicks it was flooded and would only bump start and then blubber out the excess fuel until it cleaned out . Now I just choke it and kick until it fires , or if it pops I'll turn the choke off and continue kicking until it fires . Usually takes 3 to 4 kicks cold . The bike likes VP 110 race gas mixed in with high octane pump gas ( 2 gal. VP , 3 gal. pump ) . It may also be possible that since you just rebuilt it and the piston and ring (s) aren't worn in yet there might be some compression loss/blow by to deal with . If you painted the frame for your resto , make sure you have good ground contact for the coil and engine . Sand or grind paint away to make sure . Good luck and let us know how it goes .

 

[bmasho]

Ditto on checking all the grounds - engine to frame, stator to coil, coil to frame, and make sure the kill button is not partially grounding out. Any of these could cause poor spark. If it turns out to be a bad motoplat, it is usually the stator and not the coil. Vance Smith in Michigan can rebuild them fairly inexpensively. He is at (810) 231-3359 or vtssmith@yahoo.com

 

[Picklito]

If you painted the frame for your resto , make sure you have good ground contact for the coil and engine . Sand or grind paint away to make sure.

Yup Yup.

 

[metalhof]

Try to bump start it . My Mag was a terrible starter until I went to an Mzb ignition and a Mikuni carb . With the Bing , if it didn't fire after the first 3 or 4 kicks it was flooded and would only bump start and then blubber out the excess fuel until it cleaned out . Now I just choke it and kick until it fires , or if it pops I'll turn the choke off and continue kicking until it fires . Usually takes 3 to 4 kicks cold . The bike likes VP 110 race gas mixed in with high octane pump gas ( 2 gal. VP , 3 gal. pump ) . It may also be possible that since you just rebuilt it and the piston and ring (s) aren't worn in yet there might be some compression loss/blow by to deal with . If you painted the frame for your resto , make sure you have good ground contact for the coil and engine . Sand or grind paint away to make sure . Good luck and let us know how it goes .

Have already went back and removed the front motor mount and completely ground the paint off to bare metal, same as the coil mount tab. What would be the proper starting technique from cold for my best chance to try to start this thing? Do I use the tickler on the Bing? Should I try to prime it by rocking back and forth in gear? I want the best chance to get it to fire without flooding it.

Also, BMASHO, thanks for the link for Vance Smith..I will email him my ohm readings and see if he thinks it is bad.

Ill try to start again after work today!


Thanks for all of the input.

Greg

 

[oldhuskychuck]

you can install small clear hose on the over low so it wont ruin your paint, but yes, hold the trickler down till it pukes all over,
then kick the crap out of it.

 

[hvaloz2]

Feel like an amateur here...but I finished up completely restoring a '74 250 mag a couple of weeks ago. Since then, I have not been able to start the darn thing. Have pretty much (maybe) pinpointed it down to being a bad Motoplat, but not sure and hate to shell out the bucks if not needed. I have pulled the carb several times and recleaned, everything is good there, has all stock jetting. Seems to be getting fuel but not much on the plug after kicking extensively. Seems to get fuel if I open the throttle and overflow the carb with the Tickler. If I pull the plug, I get spark, but just seems like it's intermittent, and only really good spark with a really hard kick, but not every time. Was told this is typical of the Motoplat, but just doesn't seem right. In checking what I can check on the ignition, Im getting 300 ohms from blue wire to ground, 16 ohms between black and blue wire, and 6000 ohms from plug wire to ground. This doesn't match the readings that i've seen on some websites, but not too far off. Ive got compression (new rebuild), spark (intermittent), and fuel....but, not even as much as a fire, or an attempt to fire. Even pulling plug and dropping some gas directly on top of the piston, I get not even an attempt to fire. I double Checked the timing and it is set at 2.5mm from TDC, which should be correct. Am I doing something wrong, or am I missing something?? Also, with using the tickler, should the bing carb just dump gas right out the overflow and out the bottom of the bowl onto the freshly painted motor??? Seems like a poor design. Any ideas? Im getting frustrated and don't know where to go with this. As it sits, it pretty to look at, but not much fun!!!

the fuel

 

[metalhof]

you can install small clear hose on the over low so it wont ruin your paint, but yes, hold the trickler down till it pukes all over,
then kick the crap out of it.

The overflow on the bing is just a small hole in bottom of the carb bowl, no hose nipple. Also,,, so close to the bowl drain bolt that it would be difficult to modify it to use one.


When you say the fuel, do you mean the octane? What should I run in this. I mixed up a half gallon of 87 octane at 32:1, and that is what im trying to start it with. Using jut cheap 2 stroke oil to break the motor in, then planned on switching to yamalube,, as Ive always ued in my 2 stroke stuff. I was always told not to use synthetic oil for break in, for it is too slick and the rings will take a looong time to seat? Any suggestion on what to run and at what ratio would be helpful! thanks!

 

[Picklito]

I keep checking this thread, hoping for the "SHE RUNS!!" post. No love so far, eh? A quick easy test is to shoot some starting fluid into the plug hole and see if she'll run for a few seconds. Even a pop will help you diagnose.

Most of these two strokes will run fairly well on pump gas, but I always buy the highest pump octane I can get. Around here that's 91. But I doubt having 87 is why your bike is not starting... unless the gas is old. Gas tends to lose the more volatile components first, and gets hard to start, even if it'll sometimes run ok once you do get it started. Make sure it's fresh fuel, and go on with your troubleshooting. 32:1 is fine (but why the cheap oil? See oil comments below...)

Only a couple of my two strokes need more than 91, and it's 'just a bit' more than 91, so a touch of race gas mixed in really helps them run their best. Not many two strokes have the same race fuel requirement as pumped up four strokes do. Again - I do NOT think that's why your bike is not starting.

You've either got a weak spark, or you've gotten the motor fouled with gas and or oil from all the kicking so far (or from the actual assembly - lot of assembly oil is good, but too much can make them hard to start initially). It can be difficult to get even a well broken in motor back on track once that happens. Sometimes it takes several rounds of taking the spark plug out to clean/dry it, kicking the motor over with the petcock off and plug out to air it out, plug back in, more kicking, plug back out, more drying, etc. Sometimes I've even turned the bike upside down and let it sit for a day or so! If the bike IS flooded with fuel (if you could somehow "know" that) you need to turn off the petcock, hold the throttle WIDE OPEN and kick, kick, kick. Clean plug, reinstall, wide open, kick, kick, kick, repeat. Once it fires it will blubber and billow out exhaust and can take several seconds to clean out or keep running. If it pops then dies - take plug out again and repeat. A clue... USUALLY, if the bike is not starting because it's loaded up with fuel, the plug will get VERY wet during the kicking attempts, easy to see when you pull the plug and look at it. Also - do you have a good plug gapped to .024"?

Weak spark could be from several things. If you're confident that you've got clean grounds and a good coil, you could be fighting a flywheel that's lost some of its magnetism. They do that. Has it been clunking around in a box, knocking against other heavy engine pieces? They can be remagnetized, but it doesn't sound like you need to do that yet. You should AT LEAST be able to get that motor to go POP!

One more thing... timing. Are you sure you set it to 2.5mm BEFORE top dead center? I've see guys do it backwards and end up AFTER TDC.

Oh, heck... might as well spout out one more opinion while I'm here! There is no need to use a "cheap two stroke oil" to break it in. Yamalube would have been fine, as would any of the current synthetics. The idea about synthetics being too slippery for break-in just didn't pan out, and it's safe to go there right away.

 

[metalhof]

I keep checking this thread, hoping for the "SHE RUNS!!" post. No love so far, eh? A quick easy test is to shoot some starting fluid into the plug hole and see if she'll run for a few seconds. Even a pop will help you diagnose.

Most of these two strokes will run fairly well on pump gas, but I always buy the highest pump octane I can get. Around here that's 91. But I doubt having 87 is why your bike is not starting... unless the gas is old. Gas tends to lose the more volatile components first, and gets hard to start, even if it'll sometimes run ok once you do get it started. Make sure it's fresh fuel, and go on with your troubleshooting. 32:1 is fine (but why the cheap oil? See oil comments below...)

Only a couple of my two strokes need more than 91, and it's 'just a bit' more than 91, so a touch of race gas mixed in really helps them run their best. Not many two strokes have the same race fuel requirement as pumped up four strokes do. Again - I do NOT think that's why your bike is not starting.

You've either got a weak spark, or you've gotten the motor fouled with gas and or oil from all the kicking so far (or from the actual assembly - lot of assembly oil is good, but too much can make them hard to start initially). It can be difficult to get even a well broken in motor back on track once that happens. Sometimes it takes several rounds of taking the spark plug out to clean/dry it, kicking the motor over with the petcock off and plug out to air it out, plug back in, more kicking, plug back out, more drying, etc. Sometimes I've even turned the bike upside down and let it sit for a day or so! If the bike IS flooded with fuel (if you could somehow "know" that) you need to turn off the petcock, hold the throttle WIDE OPEN and kick, kick, kick. Clean plug, reinstall, wide open, kick, kick, kick, repeat. Once it fires it will blubber and billow out exhaust and can take several seconds to clean out or keep running. If it pops then dies - take plug out again and repeat. A clue... USUALLY, if the bike is not starting because it's loaded up with fuel, the plug will get VERY wet during the kicking attempts, easy to see when you pull the plug and look at it. Also - do you have a good plug gapped to .024"?

Weak spark could be from several things. If you're confident that you've got clean grounds and a good coil, you could be fighting a flywheel that's lost some of its magnetism. They do that. Has it been clunking around in a box, knocking against other heavy engine pieces? They can be remagnetized, but it doesn't sound like you need to do that yet. You should AT LEAST be able to get that motor to go POP!

One more thing... timing. Are you sure you set it to 2.5mm BEFORE top dead center? I've see guys do it backwards and end up AFTER TDC.

Oh, heck... might as well spout out one more opinion while I'm here! There is no need to use a "cheap two stroke oil" to break it in. Yamalube would have been fine, as would any of the current synthetics. The idea about synthetics being too slippery for break-in just didn't pan out, and it's safe to go there right away.

Well,,,,, still no love but now have high hopes! my dad borrowed a couple different stators and coils from Forrest Stahl down the road to test before I spent the money on the Motoplat repair. When we pulled the flywheel, there was about a 1/2" piece of wire brush stuck in there ! Reinstalled and spark is excellent, and nice bright spark every kick. So, reinstalled tank and hooked everything back up, put gas in it turned on the petcock, and fuel overflowed the carb and just started dumping fuel into the cylinder (and everywhere else), flooding it instantly. SO here we are, I think shes ready to fire, but now the carb is pullled and dad's gonna run over to Stahl's and grab a new float needle while Im at work today and we'll go from there. Also drained the case oil for it was loaded with fuel! So hopefully sometime this week ill be firing this thing up. Thanks for the info and help..Oh, an I figured the break in oil thing was a wash, I just remembered the guy at the Honda shop when I was a kid telling us that when we picked up the parts to rebuild an old KX125.

 

[Husq.fleet]

I agree with Picklito on the "break in oil". Fresh engine start up is the most critical time for adequate lubrication. Having fuel in the case oil makes me suspicious of a crank seal problem? Having a bunch of gas in the crankcase is a pain to get out as described above. When I have an engine down, cases split I have drilled and tapped a 1/16th pipe plug in mine to be able clear out the crankcase if needed. I had that reoccuring problem with my 500. If you have a weak spark with a plug gapped at .024 try .018. Going to a tighter gap takes some load off of the coil , less energy to jump the gap. It will also advance the spark timing a little.

 

[metalhof]

OK,

hadnt messed with my bike for a couple of months. FINALLY Got my bike fired up yesterday. It Took dropping some fuel on top of the piston, then fired up after 3 kicks. Ran like a top. Idles perfectly. Took around the yard, revs smooth, no missing. Seems to be absolutely nothing wrong with it when its running......Problem is, I shut it off....immediately try to fire it back up....nothing. What am I doing wrong with this thing? What could the issue be? The only thing i can thing of now is that its sucking air somewhere, and kicking it alone will not pull fuel out of the carb, but after starting it by putting gas in the cylinder, the air leak is not big enough to keep it from running? Any ideas?

 

[Ron]

I hate to admit this but...
When we got ready to fire up the 390CR I just finished, I kicked it a dozen times and nothing happened. My son kicks it 3 times and it fires right up.
We each rode it up and down the street a couple times and shut it off. After about 5 minutes I tried to start it, 4-5 kicks nothing, my son gets on and fires on 1 kick.
It has to be kicked fast enough to spin the motor and generate some spark.
I just can't kick it through fast enough. Good thing it's his bike.
Ron

 

[Parh 474]

There shouldn't be any way fuel can get in the trans oil. Sounds like you have a mangled centercase gasket. You may have to split the cases again. That will also cause it to suck air, run lean, and not start. Are you set up to pressure test the motor?

Craig

 

[Old Geezer]

I hate to admit this but...It has to be kicked fast enough to spin the motor and generate some spark.
I just can't kick it through fast enough. Good thing it's his bike.
Ron

Boy, does that sound familiar. My 500XC with it's short little kicker, high compression, and tall saddle height...and my scrawney little left leg...I just can't get a good strong kick unless I'm standing on something to raise my height another foot or so and side kick it (and I'm 6'1"). Of course, it would help if I got off my dead ass and fixed what I think is a flywheel-side seal leak.

 

[Ron]

A leaky side seal can turn into an expensive repair that would have been pocket change, especially given how easy it is to replace.
Big bonus if it makes the bike easier to start.

 

[metalhof]

There shouldn't be any way fuel can get in the trans oil. Sounds like you have a mangled centercase gasket. You may have to split the cases again. That will also cause it to suck air, run lean, and not start. Are you set up to pressure test the motor?

Craig

There actually wasn't any fuel in the case. Back several months ago, It was just flooded out so bad and had a ton of fuel under the crank. Every time you would kick it over fuel would slosh around and even gurgle out around the exhaust port. This was due to my EXTREME overuse of the tickler and about a thousand failed attempts at kickstarting back when i first tried to get it running. The last thing i did before i let it sit for the last couple of months was take the exhaust off, pull the plug, put it in second gear, and ran around the yard with it trying to pump out all of the fuel. This seemed to help a little. I pulled the intake manifold off and cranked the piston up to the top and let it sit that way until last sunday trying to dry it out. Im starting to think starting this thing is just a matter of finding the right technique..........Normally, I would think that low compression, bad crank seal, etc could be an issue, but the only thing that I did not do myself on this bike was the motor. My dads friend down the road by the name of Forest Stahl completely rebuilt this engine. I consider him probably one of the world Husqvarna experts, and could probably rebuild this motor in his sleep. I am pretty confident that this motor is about as perfect as one could be. BTW: Having him available for parts/information throughout this restoration sure made things easier! I think the first thing ill try when i give it another shot is lean the bike over until fuel runs out of the overflow (which really shouldnt be any different than the tickler), put it in gear and rock it back and forth several times to prime it up, and give it shot. I thought about taking a spare intake manifold, putting a small fuel line nipple on the bottom, running a "Tee" of of the fuel line, and putting a primer bulb on it to give it a few squirts of gas on a cold start. I wonder if this would work? Basically the same setup as any snowmobile, and would essentially be the same thing as pulling the plug and dropping gas on top of the piston.

 

[halffast]

A badly worn carb slide can allow air to flow around it instead of under it and possibly cause the problems you are having . The bike would still run OK once started . Have you tried holding the throttle partially or fully open during starting attempts ?

Swap the Bing for a 36mm Mikuni and install Boyesen dual stage reeds while you are at it . This will go a long way toward relieving a lot of headaches and frustration .

 

[metalhof]

You wouldnt happen to have a link or any info on the Mikuni That i should swap for would you. I would assume this would mean changing the intake manifold as well?

 

[metalhof]

A badly worn carb slide can allow air to flow around it instead of under it and possibly cause the problems you are having . The bike would still run OK once started . Have you tried holding the throttle partially or fully open during starting attempts ?

Swap the Bing for a 36mm Mikuni and install Boyesen dual stage reeds while you are at it . This will go a long way toward relieving a lot of headaches and frustration .

Messed with the bike again today. Still cant kick it to fire, but found out I can roll it about 10 feet, hop on the bike, pop the clutch in second gear, and she fires right up almost instantly. It fires up so easy this way, almost as soon as you pop the clutch?? Seems with this being the case, kicking it should be as effective, but its not. AT this point, Im happy with easily being able to bump start it**************************************** but still......just doesnt make sense to me. The only thing I can think of now is that maybe the clutch is slipping a little when im kicking it, not allowing me to get a full kick on the thing. It seems like the motor only gets about one stroke of the crank for every kick. Is that normal?