Loud screeching with clutch pulled

[SpecializedMountainMoto]

hey all,
Recently picked up a motor locally that is supposed to be a pk-80, but had a sticker on the clutch cover that read CDH. Anyway this thing makes the most disgusting screeching when at idle with the clutch pulled. I thought it was the clutch but I don’t think so anymore. The guy I purchased from said this is normal, but any of the motors I’ve built in the past never had this.

 

[SpecializedMountainMoto]

It is in break in period now but still, sounds really bad.

 

[crassius]

FIRST AND QUICKLY - open clutch cover and check for rub marks on inside of cover AND take out spark plug so you can get grease onto small bevel gear and turn motor to spread grease evenly around the big gear - don't use so much that any grease gets on clutch

CDH makes a good motor, but for several weeks, someone at the factory was forgetting to grease them

 

[SpecializedMountainMoto]

thanks, will report back. Taking the spark plug out is just to release the compression so i can hand turn the motor correct?

 

[Krug]

That would be correct. My first thought is that, since the noise only occurs when pulling the clutch, if there are no marks on the inside of the clutch cover per Crassius' suggestion it's most likely going to be a severe lack of grease on the clutch mandrel/bucking arm/bearing assembly. Definitely give that a look.

 

[SpecializedMountainMoto]

thanks Krug- do you advise of squirting some marine grease down the clutch cable guide hole for this?

 

[Krug]

You can do that, yes, but be careful not to put too much down there - I've heard of people getting it onto their clutch pads that way (somehow!) and I'm not entirely sure of the efficacy of that method. As long as you put a moderate amount of grease in that hole, there's likely no harm done. My preferred method is to take off the sprocket cover, remove the bucking bar and bearing, and pack some grease into the hole. Putting the bucking bar and bearing back in will force out excess grease which you can use to grease up the outside end of the bucking bar and contact area of the clutch mandrel. While you're at it, take out the clutch mandrel from the sprocket cover and grease it up! Any medium to heavy grease will do - my favorite is Super Lube multipurpose synthetic. It's even food grade!

 

[Greg58]

While putting grease in the clutch mount hole will lube the bearings it will not get to the bar and ball. You'll have to remove the sprocket side cover to lube them.

 

[SpecializedMountainMoto]

Ok so I just put grease into the hole for the bucking bar with it and the ball removed. I have not yet squirted down the guide hole. So I started the motor with the clutch cover completely removed and the new grease in the bar hole- same sound no change. But I also just discovered something pretty strange. The sound goes away with the choke on. WTH

 

[SpecializedMountainMoto]

Must be the gear harmonics, exactly at the idle rpm (which happens to be far to high right now without the choke)

 

[Krug]

That's bizarre. Have you identified or tried to pinpoint the location the sound is coming from? Perhaps it's the clutch plate rubbing against the clutch pads at higher RPM?

At the least, you've probably helped improve the longevity of your bucking bar with that grease. It's one of the first things I do to an engine, along with greasing up the bevel gears. No grease on the bevel gears will cause them to wear rapidly.

 

[SpecializedMountainMoto]

Seems to be related to rpm, I did just do the grease of the gears with the plug out, no change. I’m going to try getting some grease down the guide hole next but I think it’s just bad gear machining and affecting that rpm range with harmonics.

 

[Greg58]

I had one engine that whined bad when new, mine was when I was slowing down close to idle. After not finding any problems I just kept riding, after a few long rides the noise was hardly noticed.

 

[crassius]

clutch hub bearings only turn when clutch lever is pulled, so might be there too - nothing can be done about that if noisy

 

[Greg58]

Here's the clutch hub bearings.

 

[SpecializedMountainMoto]

thanks guys, gonna give her a few long rides and see if it persists