Auto gear changing

my auto likes to change gears at quite low revs, I have had a chat with another long time owner and we think it would be weak or the wrong springs, is this right? If so are springs available and I believe they are or were available in different rates(colour coded) Any advice gladly recieved.

More like broken springs or not enough spring tension.
Later George

I assume we are talking about the springs on the shoes but not the ones on the crank. I have never had a problem with them, yes you can change springs and change chain sprockets to get different effects. You could change the weight of the shoes as well if so inclined. Perhaps one of them is broken. All my maintance has been with the first gear.

I once went to a liquidation auction of a spring maker. It appears they quench springs in liquid salt. It kind of looks simpler than making gears, not sure if anyone is making new springs done right.

Fran

Fran

They mainly used red for 2nd and third gear rated at 12kp and green for 4th gear rated at 8 kp.
I changed my 2nd gear red spring from 12 kp to 17 kp and the motor revs out a lot more before it changes to 3rd gear.
There is a guy on ebay selling 17 kp springs.

The origional post didn't state whether we were to discuss three or four speed automatics. Though I just rode my 420 (4speed) and 430 (3speed) without experimenting with the springs it is my understanding that when the higher gear pushes enough then the lower free wheels. Wouldn't a stiffer second gear spring make it rev more in first. These things can be pretty dangerous my 420 stood up and attacked a 3 inch diameter tree and I still think I had twisted the throtle closed. If anything makes it less likely to stand up that might be what you ought to start with. They work real good in the snow.

I think you should take the tranny apart, replace weak springs with the right colors and look for damage and anything worn out before something breaks and messes up other parts. It really doesn't take very long to get it all apart and inspect all the bits inside.

fran...k, Your experience with your 420 going WFO by itself is not unique. The 420AE that I have now has done that twice. 30 years ago my brother in law rode it to a party one afternoon. As it was starting to get dark late that afternoon he kick started the bike and shifted into gear. As soon as he got his hands on the bars the bike took off heading toward the hosts closed garage doors. John instinctively rode the wheelie and managed to miss the garage and ride down the driveway. All in attendance were amazed and he never told them he was scared sh..less.

After sitting in his barn in Hew Hampshire for 25 years he sent me the bike with a locked up engine. After cleaning out the engine and replacing the seals and corroded carburetor and ignition stator I got it started but was having trouble starting it and keeping it running. (I finally discovered that I had not cleaned out the piston ring groove well enough so the ring wasn't sealing.) But anyway back to the story. While I was still in troubleshooting mode one day I started the bike in the front yard and all of a sudden the engine went WFO. Luckily I had not put the bike in gear. I made sure the throttle was closed and mashed on the kill button but that didn't stop the engine. I pulled off the spark plug cap and that didn't stop it either. I think I also tried putting my hand over the exhaust pipe and closing the petcock. Well it finally stopped and has never done it since, but I never figure out why.

Some weeks after that event I did a leak down test and discovered that the rubber intake spigot was rotten and leaking. The carb is also pretty old and slightly worn bore (I just ordered a replacement off a snowmobile and will post my results of swapping it on).

I am not sure what causes this. Maybe the floats get stuck in the carb and drain too much fuel in to the crankcase. Then a hot spot on the spark plug autoignites the fuel. But with the throttle closed (I assume it was closed) it has to be sucking lots of air from somewhere to rev out that high. But where?

In my instance I was on a trail perhaps twisting a little more than I should have been and it seemed as it lept up after I had shut the throttle, just a fraction of a second later. I have experienced that two stroke run away on another bike it might need a piece of carbon to come off the piston and get stuck in the spark plug and stay red hot while the base gasket leaks or something like that.

It doesn't take that long to take it apart but you have to pull the first gear clutch off to get the big drum out and should re torque the first gear clutch's nut a few times in the first few hours after that. More of a pain with the water pump ones and still that taper often welds itself together.

You might want to take a look at the holes in the bobweights where the springs go and check for ovaling that will take the tension off the springs and they will engage faster,my friends have Autos and that is one of the problems. They don't usually have any broken springs on the 2,3,4 cluster.

Good point about the holes for the bobweight pins. One of my springs broke inside the drum assembly (can't recall which gear 2, 3 or 4) and it broke off one of the ears that have the hole for the pin. I had a buddy weld on a new ear, machine it down, drill the hole to size and heat treat it. Has been working OK since (knock on wood).

Huskydogg,
I am interested in your auto parts...

Norman