Gidday. I have just replaced the sprag gear after it detonated due to a low voltage Boyer incident...you know how the story goes. However , when I crank the starter, it sounds like all hell is breaking loose inside the primary. Very nasty. I have taken it apart 3 times since and i can;t get rid of the horrible gnashing, grinding noise. I have fitted one of the smaller starter units from Old Britts, I think. Eventually the motor catches and it works but where do I start to get rid of the noise.
I still have this loud deep knock from in the primary when i just blip the throttle. I wonder if this is related. Any ideas please?

hillbone wrote:However , when I crank the starter, it sounds like all hell is breaking loose inside the primary. Very nasty. I have taken it apart 3 times since and i can;t get rid of the horrible gnashing, grinding noise.

That noise could be caused by the overload backfire device slipping?

As it makes an awful noise when it does slip, and if it is set a bit too loose then it could be slipping under normal starter operation?
The amount of slip torque can be adjusted, however don't just tighten it down, as then it may not slip at all when the engine does kick back, and the result of that could be another broken sprag unit. So I suggest you check the slip torque, as it needs to be set to 50 ft lb.

Here's how: http://www.oldbritts.com/e_start_backfire.html

awesome!. thanks. I have never dissassembled that part. it has always been just 1piece. gotta love the Old Britts site.
away now for a few days. i'll get syuck into it later this week. report back. Cheers

Fred at Old Brits will test and adjust your backfire assembly for you (his test rig requires a few used parts that you may not have). Takes a few days in the US for the part to complete the round trip. If you're abroad (I didn't see your location) using Fred will add a a few weeks to the turnaround.

Are you sure the primary chain is truely mounted on both double sprockets? Such an error is easy to make, especially on the clutch sprocket (I'm embarrassed to say), and results in the same awful sounds on starting and blipping.

I had a similar primary noise. Especially at low throttle opening and when I blipped the throttle. Turns out that years ago when I had my motor bored 20 over for the second time, I put the spacer behind the clutch basket in backwards and did not have the recessed portion of the spacer over the circlip. There was a very low speed wobble in the clutch basket that was not a good noise. It disappeared at about 1100 rpm and above. Putting the spacer back in correctly cured the primary noise problem. Good luck with your issue.

Bob in Fresno

Gidday. Yes I've checked the spacing washer covers the circlip. When I take out the clutch plates the noise is not there. It probably gets back now to the back fire device not set up right. I would imagine that with the clutch plates and pressure plate out, there is not the load on the whole system. I'll bet the backfire devie needs servicing.










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thanks for the advise to send it to Fred. I am in australia and we are looking at 10 days 1 way. Too long. I will have a crack at it myself. I don't understand the tool that Fred made up , but when I pull it to pieces the concept may gel. .....maybe.

hillbone wrote:I don't understand the tool that Fred made up , but when I pull it to pieces the concept may gel. .....maybe.

If you cut some short lengths of welding rod, you can use an appropriately sized socket jammed over the pieces of welding rod which are placed between the splines of the shaft and the socket to act as the tool. That's how I did it.

To check the device up to the 50 ft-lbs of slip torque in the vice, I had a spare thrust washer, part No. 065652, and I ground it into an appropriate hexagonal shape for a socket to fit onto. They are reasonably cheap to buy/replace.

Thanks for the advise. Will do. Happy new Year Hillbone

Gidday. Just checked the back fire tension and it is set at 47lbs. Bummer! It looks as though it has been reconditioned recently as it is all in good, near new condition. Maybe I will start by checking out the Old britts starter motor. Maybe something has come adrift in there.

Operating the starter with the primary cover removed might give you a better idea of where the problem is?

hillbone, as you've had the electric start train dissembled to replace the sprag clutch, are you sure that you've assembled all of the items correctly? Not wishing to insult your intelligence or anything, but old britts has a pictoral instructional assembly, which can be found under technical articles, then go to Gear Box, Clutch, Primary & Final Drives, and it can be found in that section.

Will do again............. always sound advise mate!. I always check the idiot factor first. Love the Old Britts detail they go into.
I will start back right to matching the clutch hub and engine sprocket with a straight edge. I will get the !@#$% thing sorted. Cheers Happy New Year