Clunking when starting

[Leo44]

Hi everyone,

I recently finished putting together my 1VJ after a long down-to-chassis restoration, during said restoration I also rebuilt and replaced some engine parts, including the starter motor.

Now, whenever I start the bike using the e-start, if the starting time takes more than 3-4 revolutions, I hear this "clunk" sound for every following revoltion

The same thing gets described in this HU thread: https://www.horizonsunlimited.com/hubb/ ... rter-98882

Presumably, it's just the starter clutch that freewheels for a moment whenever the piston goes past TDC in compression stroke, gets pushed downwards faster than the starter can spin the crankshaft, then slows down, the starter then catches up and re-engages the clutch, making this "clunk" noise.

Sadly in the HU thread there isn't a definitive answer/solution so here I am, anybody has any suggestion/fix/knowledge regarding this issue? If it's an actual issue at all of course

Thanks in advance as always!
Leo

[cadno]

Is there a similar clunk or metallic noise when the bike is switched off?

[Leo44]

Is there a similar clunk or metallic noise when the bike is switched off?

Yes exactly, of course when I turn the bike off, the noise happens just once

[cadno]

That's wear in the starter sprag clutch.
You can't get the part from Yamaha anymore. It might be worth stripping it and meticulously cleaning it.
There are a few aftermarket suppliers.

[Leo44]

That's wear in the starter sprag clutch.
You can't get the part from Yamaha anymore. It might be worth stripping it and meticulously cleaning it.
There are a few aftermarket suppliers.

That's not a pleasant thing to read I guess, nor a fun thing to do, removing the sprag clutch means removing the flywheel, right? I read many times that it can be a frustrating thing

Do you mind sharing some of those aftermarket suppliers for the sprag? Thanks again

Leo

[charliext1vj]

DONT KNOW WHAT THEY ARE LIKE!!!! or even if THEY fit!

https://www.ebay.co.uk/itm/236038676775
https://www.amazon.com/Artudatech-Start ... /B091CQHTD

[Leo44]

Lucky me, I had a spare motor (presumabely low mileage) lying around and it still had the one way sprag together with the big gear and thrust washer.

This is the spare sprag, it doesn't look worn out to me but I'd like someone else's opinion just to make sure that it's worth swapping onto my bike





There is a bit of flash rust but nothing that a bit of scotch brite can't handle, plus the rust is on "non-contact" surfaces
The surfaces where the sprag rides on are free of damage/pitting/wear

[donnybach]

Don’t think you’ll tell by looking, witness marks but nothing much.
Have you run the bike for much yet though? It might be different after use, as opposed to standing some time.
I’d give it a ride for a while. A set up engine will kick easily and it’s more enjoyable so bike is useable . Then you can see if anything else needs adjusting or replacing before you rip the casings off again. You’ll no doubt be playing with carb settings for several rides, and clutch adjustment.
Weather is turning. Play with it for a bit then make any alterations when the evenings get dark.

[Leo44]

Don’t think you’ll tell by looking, witness marks but nothing much.
Have you run the bike for much yet though? It might be different after use, as opposed to standing some time.
I’d give it a ride for a while. A set up engine will kick easily and it’s more enjoyable so bike is useable . Then you can see if anything else needs adjusting or replacing before you rip the casings off again. You’ll no doubt be playing with carb settings for several rides, and clutch adjustment.
Weather is turning. Play with it for a bit then make any alterations when the evenings get dark.

Oh yeah you are absolutely right, I don’t intend on opening the casing again soon, I barely have 20 miles on the new top end, I’ll wait until the break in oil change, so around 350-400 miles or so, if the clunking is still there then I’ll think about swapping the sprag

[cadno]

I'll be amazed if it 'just goes away'
Let's wait and see...
Unless it actually breaks into pieces it'll last a long time, don't worry about it.