Starter advice

[Bjorn]

Hi guys,

Need some advice.

I just installed a starter after rebuilding the engine. The starter is turning over fine but the Bendix is engaging and disengaging. I found that this is a common problem.

Here is a video clip i made of the problem:

The starter gear/clip & spring are brand new. I measured the drag of the clip, according to the forum it should be around 6lbs. I measured 5,4 lbs.

Should I try to pinch the clip to increase the drag? Or could it be something else?

 

[Jim]

Should I try to pinch the clip to increase the drag?

Yes, I think I'd try that first. I've always thought that about 8lbs was the sweet spot?

 

[Jim]

If you do try squeezing the clip, put a drill bit in the clip and tape two of them to the vise jaws. That will bend it at the straight sections. The horseshoe section (at the bottom of the diagram) has been known to crack if you just try to squeeze it down. This will prevent that.

 

[Bjorn]

Hi Jim,

I tried to squeeze it like you mentioned. It looks like the max force I can get (clip drag) is around 6,4 lbs. (2950g).

However the Bendix is still showing erratic behaviour....

See this latest video:

Any other ideas?

 

[Jim]

Any other ideas?

Not really.

 

[Jim]

You could try putting a little "twist" in the clip. That way it would rub on the sides of the gear as well as the inside part. Might add an extra pound or two of drag.

 

[gggGary]

Don't know if running unloaded is a valid test for the in out of the gear?

 

[Jim]

Don't know if running unloaded is a valid test for the in out of the gear?

Go to "Close Caption" and "translate to English." Plugs are in?

 

[Bjorn]

Yeah plugs are in!!

 

[Bjorn]

Its a 277 now, 750cc, I was told the starter should be able to power this.

I also found a post about some shock absorbers in the starter reduction gears?
Are the really that important? I could open the other side and see. However i already found that i cannot buts them anywhere...

 

[Jim]

I also found a post about some shock absorbers in the starter reduction gears?
Are the really that important? I could open the other side and see. However i already found that i cannot buts them anywhere...

Be interesting to see what condition they're in.

 

[Bjorn]

I'll get them out.

What about the spring tension on the Bendix gear? (Not the friction clip but the actual spring).
It's new to, could stretch it a bit to give some more preload. But i don't know of that a "know fix" ....

 

[Jim]

I'll get them out.

What about the spring tension on the Bendix gear? (Not the friction clip but the actual spring).
It's new to, could stretch it a bit to give some more preload. But i don't know of that a "know fix" ....

Not 100% positive, but I think that spring is to help "kick out" the bendix gear, the opposite of what you need. Maybe try putting the old spring back in?
.... perhaps the new one is "too" strong?

 

[Bjorn]

Are they super soft and squishy, no. Do they feel like rubber, yes.

They are not broken, feel a little soft but it's hard to quantity. Doesn't feel like this could be the problem

 

[Bjorn]

Not 100% positive, but I think that spring is to help "kick out" the bendix gear, the opposite of what you need. Maybe try putting the old spring back in?
.... perhaps the new one is "too" strong?

Makes sense, what about the erratic movement of the crank, maybe when the Bendix sees to little force it's snaps back straight away?

Unfortunately there is no old clip in my possessions. I dumped the starter 10+ years ago in all my wisdom (lol) and now I had to get new parts to build it back up.

 

[GLJ]

Hi Jim,

I tried to squeeze it like you mentioned. It looks like the max force I can get (clip drag) is around 6,4 lbs. (2950g).

However the Bendix is still showing erratic behaviour....

See this latest video:

Any other ideas?

I've seen that also when when cranking over the engine with the plugs in. I think what is happening is that when you get past TDC on a compression stroke the compression causes the crank to rapidly speed up. If the starter gear does not speed up enough to match it the gear does what it's supposed to do and back away from the crank. You have to remember this is a Bendix type starter gear not overrunning. The crank turning faster than the starer gear is what backs it out.
Crank it over without the plugs and see how it does. I believe a loose spring causes more of a problem getting the gear to engage than keeping it engaged.

 

[Its been a long time]

View attachment 328759

Are they super soft and squishy, no. Do they feel like rubber, yes.

They are not broken, feel a little soft but it's hard to quantity. Doesn't feel like this could be the problem

Hard to tell from a picture but those rubbers look in great condition.

 

[Its been a long time]

I've seen that also when when cranking over the engine with the plugs in. I think what is happening is that when you get past TDC on a compression stroke the compression causes the crank to rapidly speed up. If the starter gear does not speed up enough to match it the gear does what it's supposed to do and back away from the crank. You have to remember this is a Bendix type starter gear not overrunning. The crank turning faster than the starer gear is what backs it out.
Crank it over without the plugs and see how it does. I believe a loose spring causes more of a problem getting the gear to engage than keeping it engaged.

I'm not so sure cranking with the plugs out tells you much? I recently had the starter grinding issue. With the plugs out the motor cranked fast and reliably. But as soon as I put the spark plugs in I immediately got the starter grinding and no cranking at all.

I used a new Yamaha drag spring and as supplied I got about 1.5kg drag. The spring I removed was the same. I squashed the new spring and got around 3kg drag. I've tested the cranking four times and it seems to have worked. Longer term, the jury is out.

 

[Bjorn]

Here is a video i made earlier today without plugs mounted. Please note this is before increasing the clip drag by squeezing it. The Bendix does not seem to disengage.

I need to reassemble things first to retest this.

I could rebuild the bike, however I would not like to take it apart again.... Secondly I have not had the bike fire up yet with the new engine rebuild to 277° / 750cc. I kinda need the starter because kicking is killing my leg.

 

[GLJ]

I'm not so sure cranking with the plugs out tells you much? I recently had the starter grinding issue. With the plugs out the motor cranked fast and reliably. But as soon as I put the spark plugs in I immediately got the starter grinding and no cranking at all.

I used a new Yamaha drag spring and as supplied I got about 1.5kg drag. The spring I removed was the same. I squashed the new spring and got around 3kg drag. I've tested the cranking four times and it seems to have worked. Longer term, the jury is out.

It's not a final test.
Was your starter grinding on engagement or after it started cranking?