The Infamous 75' Trick Start 850 (2010)

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Tim_S

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Aug 24, 2010
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First time poster here so please bare with me. My MK III project is coming to an end finally. The bike now has a Boyer, upgraded #6 battery cables, new battery, new sprag ($180) ouch! and a rebuilt stock starter. There was one bad field coil replaced and new brushes. The sprag engaged a couple times now nothing? I only hear the starter spinning or the gear inside the primary spinning when the button is pushed.
Has anyone wired in a relay to help out the weak switch gear? If so, I'd like to hear about it. How about a replacement starter solonoid? I don't have the four brush starter either. I know all the stories about the four brush setup and a bigger battery,,,, etc. At this point in the project I want the starter to at least turn the motor over whether it starts or not is irrelavent. Your thoughts...

cheers!

Tim_S
 
Howdy Tim and let me be the first to welcome you.

In your primary case is the anti-backfire clutch, if your starter is spinning and the engine isn't good chance that it loosened up. There is a great article on the Old Brits web site that has been referenced many time on the forum that will guide you on how to adjust the anti-backfire clutch.

My opinion of the OE Norton starter is that it is a "kick-assist" at best; CNW has a great 4 brush/field coil starter and Dave Comeau at Atlantic green has a similar starter.

Fix or adjust your anti-backfire clutch and see what you think.

RS
 
Tim_S said:
The sprag engaged a couple times now nothing? I only hear the starter spinning or the gear inside the primary spinning when the button is pushed.
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There's a chance the sprags have "tipped over" because of excess clearance between the two bearing surfaces (did you replace all three parts or just the sprag unit?) or the overload backfire assembly torque setting may need re-adjusting? And that doesn't simply mean tighten it down, as it won't protect the sprag and the rest of the starter drive against kick backs if it's over-adjusted.

http://www.oldbritts.com/e_start_backfire.html
 
I have only replaced the sprag and nothing else in there. I totally agree the starter is merely an 'assist' for that big lump. I have seen Dyno Dave's starter in action. It could probably turnover a v8 small block? :D I looked around for the parts to convert my starter to a four brush but no luck. I never thought about the backfire adjustment? Thanks for the tip! I did however double check my install of the sprag for the correct placement. The Norton Tech digest has a nice picture of that unlike the factory manual.
As for adding a relay to the system? Would that help get more juice to the starter from the weak start button? Anyone tried it?

Cheers!

Tim
 
Tim_S said:
As for adding a relay to the system? Would that help get more juice to the starter from the weak start button? Anyone tried it?
Click to expand...

No need to try it, as the button circuit simply triggers the solenoid, and the solenoid is the relay.

The starter's power supply goes directly to the starter motor from the battery through the heavy solenoid connections-so there's nothing to be gained by attempting to improve the trigger circuit. If there's any voltage loss to the starter, then it will be the solenoid causing it, and not it's trigger circuit.

My MkIII's starter turns the cold engine over relatively easily, (and there's no lack of compression) so it's not "starter-assist", although my starter has the 4-brush (not 4-field coils) conversion, but with heavier leads and a fully charged and sufficiently powerful battery any original 2 brush starter in good condition ought to be capable of proper operation.

At odd times in the past when there's been insufficient battery power available because the battery was either not fully charged or because the battery was failing, then engine compression has always stopped the starter drive from turning, I've never known the sprag to slip because the battery power was low.

If the anti backfire device was slipping, then you would usually be aware of that due to the loud rattling noise it makes!
 
Hello Tim, my Mk3 has a rebuilt standard starter which works well when the bike is cold, but I have to wait a minute or so if the motors been running. (stalling) But with a kick start and Mikuni that doesn't happen often.
A good battery and heavy leads, both positve and negative are a good idea.

Regards
Graeme
 
Because after the motor has been running the starter is an "electric assist". I assume the motor has built up some compression. I know the starter isn't 100% but it isn't a problem to me.
This is when I'm warming the motor up if it stalls, not after a trip. But I haven't turned it off then tried to start it straight away, so I don't know about that.
 
GRM 450 said:
Because after the motor has been running the starter is an "electric assist". I assume the motor has built up some compression. I know the starter isn't 100% but it isn't a problem to me.
This is when I'm warming the motor up if it stalls, not after a trip. But I haven't turned it off then tried to start it straight away, so I don't know about that.
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Sorry, but I don't really follow what you are saying? If the motor stalls, pressing the button immediately should restart the engine, I can't see why you would need to wait for any drop in compression.
 
What I said was if the motor stalls while being warmed up, and I hit the electric starter to restart it, the starter won't turn the motor over TDC.
If I let it sit for a minute it will start the motor.
I'm not going to guess why, apart from the starter isn't 100% and assuming things have expanded etc, but not properly warmed up ??????

I have not turned the bike off and restarted it again straight away after it has warmed properly and been ridden, so I don't know if it doesn't start it sraight away then.

graeme
 
GRM 450 said:
What I said was if the motor stalls while being warmed up, and I hit the electric starter to restart it, the starter won't turn the motor over TDC.
If I let it sit for a minute it will start the motor.
I'm not going to guess why, apart from the starter isn't 100% and assuming things have expanded etc, but not properly warmed up ??????
Click to expand...


Ok, but I don't ever remember that happening to mine, if I've managed to stall it with the engine cold, the starter motor has never failed to spin the engine again straight away.
 
GRM 450 said:
What I said was if the motor stalls while being warmed up, and I hit the electric starter to restart it, the starter won't turn the motor over TDC.
If I let it sit for a minute it will start the motor.
I'm not going to guess why, apart from the starter isn't 100% and assuming things have expanded etc, but not properly warmed up ??????

I have not turned the bike off and restarted it again straight away after it has warmed properly and been ridden, so I don't know if it doesn't start it sraight away then.

graeme
Click to expand...

Could it be a weak battery that hasn't recovered from the initial start?
 
My other MK III acts the same way as Graeme's sometimes on a cold start. But then it could be the battery hasn't recovered quick enough especially if eye cranked on it a bit in the beginning. I'm gonna check the solonoid too. It may be weak too. Are all motorcycle starter solonoids created equal? :? I have a spare from a 96' model triumph I could try?


Tim
 
Ok, I took the entire assembly apart again and noticed the sprag may have "tipped" as someone put it. I used some emery cloth on the large gear surface where the sprag makes contact. I only did that for giggles, just because? :( :?:
Put it all back together [fingers crossed] and it engaged ten times in a row so I'm not going to push my luck. I did however try another type solenoid and it didn't work at all. I have a lead on a prestolite starter from a HD so maybe I can get the 4 brush setup.

cheers!

Tim
 
I had the same thing happen to me I got a little thumb happy with the starter button took it apart used emery and fliped the sprag and set the overload backfire device to 50 ft-lbs acording to Fred Eaton at the Old Britts site Its been working all summer just fine Phil
 
I'm not sure where you are located Tim_S, but around here you can find a used prestolite field coil from a Harley at most any swap meet or chopper shop. You don't need anything else from the Harley. Field coils rarely go bad, so even the scruffiest one can be cleaned up and used. New brush plate, brushes, and springs are available from tractor dealers or marine dealers cheaper than the Harley aftermarket. I also prefer to replace the front bush with a roller bearing. My rebuilt 4-brush will spin my 10:1 compression cafe racer with no hesitation.
 
Ron,
Don't you need the housing the field coils go in too? Is the entire HD starter the same size with the same gear teeth count? What about mounting hole locations? Any Different? Any other differences? No one I know around here in the flat lands of Illinois has a converted motor.


Tim
 
Tim_S said:
Is the entire HD starter the same size with the same gear teeth count? What about mounting hole locations? Any Different?
Click to expand...

You still need to use the Commando armature and end mounting plate.
 
Ron L said:
but around here you can find a used prestolite field coil from a Harley at most any swap meet or chopper shop. You don't need anything else from the Harley.
New brush plate, brushes, and springs are available from tractor dealers or marine dealers cheaper than the Harley aftermarket.

What are you suggesting about Howard Rotavators Ron :?: :?: that they would be better off sold at tractor dealerships, I'm sure JOHN DEER wouldn't want to lower their handling quality :roll:
Click to expand...
 
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