automatic kick start freewheel upgrade

anyone have the information on upgrading the 390 auto to the 420 freewheel ? I see there is a service bulletin on this but I can't find anything with pictures. Also I think there should be a automatic section on the forum, I have three a 1978 390, a 1983 250 auto enduro the only one I know of,imported for a friend of Dick Burelson's and a project 390 in a 83 auto 420 frame and suspension

Which freewheel? I have several 420s and engines and I have three sorts of free wheel(sprag clutch)!!
The 420 has straight cut primary gears, the 360/390 has helical. the gear selection is different, the crankcases are different

I am under the impression my 420 has an updated one way clutch on the crank. It has bigger sort of elliptical pieces. Actually the one on the 360 seems to have been trouble free while the one on the 420 with the bigger pieces is less than ideal but I can get it started. How does yours behave? Do you have a source for these pieces for a cost similar to what one would expect from the pricing of such devices in modern electric start applications?

It jams on the crank and a surface inside the first gear clutch / primary drive gear. If the diameter of the crank is really too small has crossed my mind.

I really can't help directly however if you put up some picures of what you have with some measurements I can do likewise as I know where a did assembled 420 set up is.

Something like that ?

On the 420 AE I bought, the primary clutch was changed.
430 ae clutch was welded on 420 gear. Need to add pawls and springs
to have the same device as on 430 ae.

In the service bulletin it refers to a upgrade to the 390 crank freewheel to the 420 freewheel which I believe is like the one in the bottom picture above one piece bearings and freewheel. The problem I'm having is when taking the crank clutch off to service the trans the freewheel falls apart(fe433z) and what a pain to put back together. Has anyone used one of these kits ? I has a couple of the nos one piece bearing and freewheel combos and they are smaller id than the 390 hub . The service bulletin refers to a sleeve being used

The separate pieces with the spring thing through them is what my 420 has. It has bronze caps that act as bushings. I can see bearings and free wheel (two of one and one of the other) inside the last picture of post 5. Perhaps there is more to the update than the thing I copied Michael's picture of.

I would choose to stay with the smooth drum and the bronze shoes with the ridges at a slight angle (prior to 500 and 430) if at all possible, that is if one intends on using it much. The notches and pivoting pieces perhaps could be cut in if the freewheel system becomes hopeless. Then I have seen a pull rope starter on some pictures probably early.

Sort of off topic but I just heard an opinion that the "welding" of that taper is effected by the fact there is a keyway cut into it.

All you need to do is replace the free wheel , a new one or one in good condition-does not fall to pieces, like i said earlier the 420 has straight gears on the primary drive so you need to change your main gear box shaft into a 420 main gear clutch drum, just not worth the effort.

Thanks for all of the replies, I sure would like to see a picture of the service kit , but I can still deal with what I have , I'm hope to see Dick Burleson at the Greenville Ohio enduro and see if he has any info . Fran , what is the welding of the taper suppose to improve?

I have replaced the freewheel and the clutch drum with new nos parts they just don't seem to last that long (the freewheel) maybe my crank end is worn out of spec? I do ride these , they are a ton of fun . The 250 auto has never had a problem other than one broken spring but it is a 83 with the newer drum and engagement system

The welding of the taper is not something you want. Sometimes when pulling off the first gear clutch it is very hard because a spot weld of sorts has occurred. Note the shoes have balance holes drilled in them. I do not understand the mechanics of how such a phenomenon can occur without shearing the key but it has happened to me and others. I do re torque that as well after a few minutes and then after an hour or so.

The 420AE/AXC factory assembly tips list the torque spec for the first gear clutch retaining nut to be 65 ft/lbs. But it has the same size threads/diameter as the 430/500AE shaft nut so I use the 430/500AE torque spec of 85 ft/lbs and have not had a problem with the clutch hub working loose. Also the shaft nut on the 420/430/500autos are the same part number 161271201. I believe the 65 ft/lbs torque spec was a carry over from the 360/390 autos which have a smaller thread size and diameter. And yes, after 10-15 minutes run time re-torque the nut.

Marty

ktmal can you send pics of the 250 ae, please ?

I will post some on the site this afternoon

So far I have not had any issues with the first gear freewheel. I run 2 needle bearings and one freewheel. When I built the motor I used new shafts either side of the crank and new bearings and freewheel. It does sound as if the shaft and/or the freewheel is worn. I would just replace both for peace of mind.

pictures of the 82 250 ae I ride it as much as possible at least twice a week

Like Grouty I have changed some of my main shafts as even a new sprag would not grip reliably!

Looks like an Army engine in an 82 frame, I have an Army bike and I too like to ride her as much as possible.

That maybe what it is but it was bought new like this ,I got it from the original owner a friend of Dick Burleson's that got it from the local dealership they said he had to pull some strings to get it in the US

I got to talk to a old auto enduro racer ,he remembered the upgrade but didn't recall if it was any better, anyone with a 420 ae any problems with the one piece bearing freewheel ? like the one above listed as number 2 in the parts drawing