Weird starting/engine noise

[rs_ss350]

Sometimes when starting (more like when the engine doesn't quite start or shuts down) i get this noise that sounds like an old fashioned oogha horn from a model T. It's funny, and embarassing, but mostly i realize there some gear in there that's whirring around not engaging properly and i'm worried something bad will likely happen at some point. I've heard things about the starter clutch (new to cb750s) but from the descriptions I'm not quite sure that's it. Any ideas what to start looking at?

 

[amc49]

The starter clutches on them are well known for doing that. There are 3 springs and pins that work the one way clutch that has to lock when starter spins up and often one doesn't quite right then starter clutch slips to spin free. Can be knocking, clunking, and various combinations of it. The outside cover held on by 3 bolts often loose too and adds to the problem. Loctite the bolts at rebuild time. The springs can deform all out of shape. Engine being slightly hard to start adds to it, engine spins up a bit slow to knock clutch loose then it drops back when it doesn't start. Starter again spins free.

What oil used in motor? Those clutches really need motorcycle specific oil with zinc in it, zinc has been dropped for all car oil pretty much due to EPA regs and the replacement 'friction modifiers' are often too slippery to make a bike start doing it when it wasn't before. Change to correct oil and problem gone.

 

[rs_ss350]

I'm using honda's motorcycle racing oil...

 

[rs_ss350]

Doesn't mention zinc on the packaging. Any specific recos for my next oil change?

 

[amc49]

Often it's in the JASO (Japanese Auto Spec Org or something like that) classification on the can, different spec from our oils here. If marked as such then has more zinc in it. Motorcycle specific oils thinking got under the EPA spec since so little used in the larger vehicle population, but also why those oils have skyrocketed in price. They were allowed to keep the zinc but at a cost penalty to drive off many purchasers.

Look for the JASO marking on the container. Valvoline also makes a pretty good MC specific oil that has zinc as well. Same rating found on those cans too. You are looking for motorcycle specific oil there, car guys use it too to get the zinc but expensive.

 

[amc49]

By 'outside cover' I meant the one that bolts onto the starter clutch itself, not outside engine cover over starter clutch. You have to yank left cover to see those 3 bolts. Often they have worked loose and loctite is suggested to hold them tight.

 

[rs_ss350]

Thanks! Yes the oil is JASO MA which is the non friction modified.

gonna pull the starter clutch out to rebuild hopefully next weekend.

 

[rs_ss350]

I've seen some mention draining the oil but I'd assume the oil is all in the pan if the bike's been sitting?