'73 400 problem/question

[joe1267]

I rebuilt the carb on my wife's 73 400 and it has been running like a champ for the last few weeks. One or two pulls and she is good to go. Good compression, strong spark,correct timing etc. Yesterday, try as I might, I could not get her sled started. It coughed a few times like it was going to start but never did. Plugs are correct and new,checked and the spark is strong,fuel turned on,gas tank full. When checked by my mechanic several weeks ago, crank seals were not leaking.

Tried some starting fluid and that did not help either. I am thinking that maybe the fuel tank screen or fuel filter may be clogged. Did a forum search and it seems like I am on the right track. Am I missing anything obvious? We are supposed to get a bunch of snow this week and I want to have her sled ready for the weekend. Your help/advice is greatly appreciated.

My JDX8 ran like a champ all day long. I rode an '09 1000cc Skidoo yesterday belonging to a friend and I just about crapped my pants when I got on the pipe...

[400brian]

Will it fire if you squirt a bit of gas down the plug holes?

[joe1267]

Brian, it was a no go with the starting fluid, but I did not try fuel down the plug holes.

[400brian]

We recommend premix in a squirt bottle, starting fluid has no lubricative properties.

If you have compression, and spark at reasonably the correct time, it will fire.

If it will not fire on spray, it indicates an ignition issue.

[SpitfireKing]

100% agree with Brian..no starting fluid! Great stuff for cold seize and also for causing bad holes in pistons if timing is incorrect....butthat was on a dirt bike..lol

if you can't get it to fire with a teaspoon of cas down the sparkplug hole then time to look at those points.....or you now have a seal leaking extremely bad, but funny it would happen to both at the same time.

[joe1267]

Guy's thank you for the advice. I won't be able to try this until Wednesday, but I will keep you in the loop. With the amount of spark those plugs were throwing, I could not believe it would not fire and you are right that it is odd that both the points or a crank seal could go at the same time. Week before I put 40+miles on it and one or tow pulls to start everytime!

Joe

[JDT]

Joe any chance you got the plug wire switched around when you did the carb and checked spark??

[joe1267]

Well, I got her running. The plug wires were where they should have been. I cleaned the fuel tank screen assembly,replaced the fuel filter,cleaned my on/off fuel valve, checked/sanded down points etc. Even after that, I pulled and pulled and pulled. It would sputter and catch like it wanted to run. I even had the cord on the pull start snap. Fortunately, I have a spare pull starter I snapped on. To alleviate my frustration, I had a beer and then took my JDX8 for a spin.

Before I left, I decided to switch back to the old champion plugs, replacing the new NGK BH6S that were in it. I told myself I would only pull it 3 more times. I grabbed the pull start, gave her a yank and don't you know the damn thing started right up. It was coughing and sputtering but I managed to keep it running while I dragged it out of the garage. I jumped on and ran her up and down the lake a few times. She ran great topping out in the mid 40's or so. The old champions were a bit black when I pulled them, but I was able to restart the sled.

I can't really explain why it suddenly started as I did not find much crud in the tank screen. The old fuel filter I replaced, still looked good and the points seemed just fine. Could the old girl simply not like the NGK's? I left my camp happy and scratching my head as to why I pulled that darn thing 200 times and then out of the blue it started.

Any thoughts will be appreciated.

I am thinking of going to a vintage sled day they are having in Edinburg NY on Sacandaga Lake this sunday. Don't know if anyone lives close by, but here is the info.

http://www.sacandagasnowmobileclub.net/12.html

[Matt]

Plugs should be B8HS. It's always possible you could have got a defective plug. It happens. How far are you from Fulton, NY? The Great Eastern Whiteout is this weekend, one of the biggest events on the east coast. Show Saturday and vintage ride Sunday. A few of us from this site will be there.

[joe1267]

Matt, I am about 2.5 hrs from Fulton. I live in the Albany NY area. Would love to come to this show. Not sure I have the time to plan it last minute. May have to plan for next season.

Looks like I grabbed the wrong NGK's for the 400. Will remedy that today.

Enjoy the show. Hope there is good snow there for you....Joe

[DLDeere]

Joe,
This sounds like a problem I've had with both of my 400's and a 300. What I found was that the carb was pouring so much gas in that it was building up gas in the crank. I opened the screw plugs at the bottom of each side of the crank and ran out a couple tablespoons of gas. Happened most frequently in warmer weather after the engine was warmed up, or if it sat and idled for a while. Acted flooded but plugs were dry. Had to keep cranking without touching the throttle or choke until it started to sputter and finally run. Nice having electric start on the 400's when this happens!

Happened a couple weeks ago on my 300 when I was getting ready to go to a show so I had to leave it behind. (no electric start) Later in the afternoon my wife went out, pulled it twice and it took off. She called me and really rubbed it in!

The solution I found was to adjust the metering lever on the Walbro to even less then the book says. In fact, on the 300, the metering lever does not stick up above the carb plate. It is actually below the carb plate about .020". The book says it should be above the plate just enough so a straight edge will catch on it. I had to put it below. Seems to work well now.

Howard

[joe1267]

Howard, I appreciate the info. It seems like her sled is at times possessed! I will take a close look at the metering arm level and if she is starting hard, I will locate the screws on the motor and see if extra gas comes out. Are the plugs on the sides or the front of the motor facing the gas tank? My wifes sled had electric start, but the starter motor is shot. Guess I will have to look for a replacement starter so I don't have to pull this thing anymore. TIme to go out and ride....Joe

[DLDeere]

Possessed is an accurate description. The crank drain plugs are on the carb side. They're at the very bottom of the crankcase. The bolt heads face towards the carb. They'll be hard to see with the engine on the sled, but you'll be able to feel them and get a socket on them. You don't have to open them to solve the problem, but if you do open them and fuel drains out, you'll have a better idea of what is wrong.

[joe1267]

Thanks for the info. I rode both sleds yesterday and my wife's 400 is running strong!According to the speedo(however accurate it may be), the old girl hit 50mph on the lake! It started easy on the second pull. I was on and off it at least a half dozen times and it started on the first pull every time there after. Right now I am just going to enjoy the riding and if it starts acting up again, I will take the carb apart and lower the metering arm. Hope everyone's sled's run well for them this weekend....Joe

They do a lot of drag racing on our little lake and I always have a smile on my face when these guys with 10K+sleds want to see and talk about my old, cheap iron....

[S_Kyle]

Ive been lucky and only had to walk twice (throttle cable and nuked motor) But have passed quite a few dead modern sleds. If this "old iron" is what we want to ride and we get there and enjoy ourselves then why spend the $15 000 on a new sled. I was debating a new sled this winter but my employer made the decision when I was sent to work in a camp. Now I am glad I stuck with the classics as I have just as much fun and where can you safely ride at the speeds being reach these days.