1970 250 Cr Starts But Won't Run

New to the Forum. I am attempting to revive a 1970 250 CR. The bike belongs to a friend so I don’t have unlimited funds for the project, unfortunately. The problem is that when it starts it runs for about 30 seconds and quits. It revs fine during the time but then just abruptly dies. When I pull the plug its wet but not overly so. When I check the plug after the engine stops, I still have spark. I have replaced the plugs a couple of times trying to get it to run but that just makes it start easier.
I have replaced the main bearings and seals. The piston is stock and checks out within specs as far as ware goes. After 3 kicks I have 150 psi during a compression check. The leak down test, starting at 5 psi loses .5 psi in 10 minutes. I did not perform a leak down test before I put the Type F fluid in the tranny, my mistake. I did place the end of the crankcase breather hose in some soapy water and got one small bubble during the test. I squirted soapy water on all the appropriate locations and found no signs of a leak. I am running a Bing 54-1, with 2.83 needle (2nd position) and jet, 35 idle and 190 main. The carb slide has a slight “happy face” on the engine side, typical. It has a Super Trap exhaust but I have removed the disks to make sure that was not the problem. The ignition is a stock Bosch points ignition with new points and condenser. I have relatively good spark but it seems like it could be much better. There is good gas flow thru the inline filter with the gas cap on. There is a little “spooge” leaking at the header but not much.
I originally thought this was a too much fuel problem but am now beginning to wonder and went to the above jetting with not much change. There are several trains of though on what acceptable on a leak down test but I don’t think .5 psi loss in 10 minutes is causing the problem. I just put points in a Rickman Zundap 125 today for a friend and the spark off the spark plug was incredible and way more than the Husky’s. Any thoughts?

Are you using fresh fuel or fuel left over from last fall?

Fresh fuel, regular pump gas, Motorex 32:1

The Femsa system on my 72 450 killed me. Took me thru highs and dirt nap lows , finally sprung for the Vape (formerly power dynamo) ignition and Never looked back. It's reliable enough that I'm going to try some vintage racing this season, from the rear of course! Good luck!

Have you installed a new float valve in the carb and set the correct float level? If you have then probably a week ignition. Hope this helps.

Marty

Sounds like you've done your home work on this one. Kudos on the detailed description. I agree that 1/2 pound leak down in 10 min is not the problem. If the carb was thoroughly cleaned i.e. carb cleaner over night and blown out with compressed air then I'd look to the ignition for a possible cause. Bosch ignition is pretty straight forward and from the sound of it you have eliminated points and condenser. The only other electrical components left is the coil and maybe a weak magneto. With a Bosch I'm assuming the ignition has the plug wire coming out of the side case verses coming from under the tank.

One of these doodads will allow you to watch the spark for the 30 seconds that it running to see if the spark fades or stops completely when the engine dies. The spooge tells me that fuel/oil mix is continuing to flow after the engine dies indicating electrical failure and not fuel.

Thanks for the suggestions. Yes new points and condenser. Plug wire comes from the coil under the tank. Since I’ve been working in it’s its never had that “fat blue spark”. The owner has another engine so I’ll start swapping ignition components to see if I can improve the spark situation. I do have one of those “dodads” So I can try that to. I’m on vacation so it will be a week or so before I can post any outcomes. I assume the Bosch on this bike is capable of producing a “fat blue spark”.

Crash, were do ya get one of those, and what is it called?

https://www.ebay.com/sch/i.html?_fr... Ignition Tester Automotive Car Detector Tool

My Femsa had a break in the magneto coil winding. Would just stall abruptly then restart. Very difficult to trace. Finally rewound it by hand using new copper wire. Still working.

Steve, I’m planning to check that when I get home at the end of the week. Steve or Crash should I have a fat blue spark from this ignition if all is good?

Ideally but it should still run even with a weaker orange spark unless the plug is being overcome by crankcase oil. I know you replaced seals and gaskets but I once had a new crank seal leak. That motor also spewed exhaust spooge and when combined with a weak spark a new plug can fail.

Makes sense. I’m going to attempt a better spark then see what happens. I am getting a little kick back at the kicker so I’ll check the advance again too. Thanks for the help!

Update:
I have replaced the secondary coil (spark plug coil) and that resulted in a much-improved spark. I have used a Buzz Box to set the advance. Unfortunately, if I can get it to start, it runs and revs fine for about 30 seconds and then begins backfiring big time thru the carb, spitting spooge from the exhaust manifold area and slowly becomes non responsive to the throttle then dies. When I pull the plug its black and dry. I have duplicated this problem twice. I have rechecked the float and float needle and they are set correctly, confirmed point gap and advance. Help!

Something wrong with the ignition still, coil, points, condenser, wires to and from, clean the carb and run from a bottle not the tank, also change the spark plug every time till you get it right. You're giving me nightmares about my little Indian that thing was a huge pain in the ass but eventually........ I replaced everything!! not everything just the o-ring on the choke, was letting air through and leaning the mixture and the spark plug ,would run for a few minutes and then die. if I revved it I could keep it running but as soon as I pulled the throttle off it would die sputter and die. Good luck

Now that I think about it the automatic was giving me trouble the other day, I hadn't ridden it very much but I went out and tried to start it and it would not start.I kicked it 20 times, I've learned if I have to kick a bike 20 x change the spark plug hope that helps.

Today I removed the clutch cover and removed the drive gear from the crank and re did my pressure test just to confirm it wasn't the wet side seal leaking. I should have done that when I reassembled the engine. It all checked fine so I can eliminate a seal issue. I have been running from a bottle with filter. I do think it starts easier with a fresh plug, guess I'll order a case of them.

At this point it sounds like an ignition problem. The back firing through the carb tells me the plug is igniting at the wrong time. Steve J's post may be worth looking into. Since it runs okay for 30 seconds maybe a broken wire in the primary coil looses conductivity after the juice has begun to run through it. Also I've read of instances where the kill switch will intermittently malfunction.

Yes, it was an ignition issue! It now starts cold on the 2nd or 3rd kick and on the first kick once its warm. The story: I had two coils, one new (universal 6v/12v points or CDI) and one old (FEMSA). I replaced the points and condenser and installed the new universal coil. I wasn’t impressed with the spark from the new coil and it was very hard to start if it would start at all. I switched to the old FEMSA coil and it had a better visible spark, however, that’s when I started getting the backfiring issue. Of course, in between I reset points, adjusted the advance and changed plugs trying to figure it out. I was able to get it running for a little longer the other day so I hopped off and looked at the points and they were arcing with a big blue spark. I had bench tested both coils already, the new one had 6.4 ohms of resistance and the old one 4.6. I did not bench test the new condenser before I installed it. I pulled the condenser and it was dead, I pulled the old coil and it had 65 ohms of resistance. I replaced the old coil with the new one and put in an old condenser that bench tested ok and it fired right up and runs great. I assume the old coil went bad, which most likely took out the condenser; hence the run for 30 seconds then backfire like crazy. I think I hit the sweet spot for the ignition settings and Bing 54-1 carb. In case anyone is curious I am running a 35 idle (1 1/4 turns out), 185 main and 2.85 needle and jet, 2nd clip position (thanks Charlie at Bing), 32:1 mix. Thanks to all of you for the advice and support, it helped immensely. It was my first experience with a Husky and I think, from reading the blogs, I was convinced it was going to be a bear to start no matter what. I also put too much reliance on the quality of spark and not enough on science. Now on to my own projects, another 70 250 CR and a 1976 WR 360. The 360 will get an electronic ignition!.

I'm confused, are you referring to two "old coils", the old secondary and then the old primary?

In any event I'm glad to hear you got it figured out.