clunk

[fossilrider]

OK guys, I've got one for ya. Just finished a complete resto on my '74 Super Rat model 98 and the little gem started on about 2nd kick and ran like a champ. This was about a week ago. Then I noticed a gas leak, and I discovered that it has rusted a small hole behind the rear mounting tab on the tank. Why in the world did they leave that little slit open for dirt and debris to collect? Of course the tank has just been painted and looks great, so I just JB welded the little gap and I (or whoever might decide to repaint the tank at some point), can address that issue then. Shouldn't be a big deal to fix if the tank is going to be repainted. Anyway, on to my issue now: I rode the bike 100 yards up the street and back and it ran like a champ. After parking it, I noticed the leak next day. So, after epoxying the leak, I thought I would do another test ride since I have decided to sell the bike and have it listed. I kicked it a few times and it fired right up, but then died. This happened several times then I was able to keep it running. I sat on the bike letting it warm up then started to take off for the ride. The bike died again and when I started kicking it again I heard a "clunk" like metal to metal, somewhere in the engine. I pulled the clutch cover off and everything looks good so I pulled the head to be sure the piston wasn't hitting something, although this sounds more like steel hitting steel, not aluminum. Piston and head are fine. I assume I am going to have to tear the engine back down and have a look inside. But before I do that, does anybody here have any ideas? I went through the engine completely ( bore/piston/rings/rod/mains/seals, etc. Thanks for any ideas, before I tear into it. Steve

[fossilrider]

To add to my previous email, sometime it will kick through and it is normal and I can slowly push the kick lever and nothing hits. Very strange!

[thrownchain]

Check to make sure your flywheel is tight, that would change your timing and cause starting issues.

[fossilrider]

Thanks for the reply. This, when it happens, is a solid metal to metal loud sound. The kick lever swings through its arc and suddenly something hits something and the lever stops. But it's weird that I can slowly cycle the lever through, turning the engine over, and it acts normal.

[dirty_rat]

Could be worn parts in the kick start system (worn roller holder, worn cam surfaces on the kick shaft, damaged or cracked kick gear) or something loose in the transmission. Sounds like it's time to split the cases and examine what you have going on in there.
Kicking it slowly doesn't put much tension on the parts so the problem might not show up by doing that.

[Bullfrog]

I'm mulling . . .

. . . but first steps for me would be to pull the side covers and check magneto side and clutch side for something amiss.

Ed

[fossilrider]

Well, I pulled the engine, after removing the side covers and seeing nothing amiss. I split the cases and went over everything with a fine-tooth comb. Nothing, except, the horse shoe shaped spring around the kicker shaft that keeps tension on the shaft so the ratchet/drum/shaft will work properly was not installed correctly. That spring has a narrow closed end that obviously is supposed to go in a slot in the case to keep it from spinning. I can't believe I didn't install it correctly. But, I'm not sure that could cause the issue I'm having. The spring (called a kick roller retainer hold snap/ item 31/ part #904715 in parts manual). What do you guys think?

[fossilrider]

I think I just had an epiphany. After thinking about that last post I thought through how the kicker mechanism works and if that part, that was supposed to be held in place by being in that slot in the case, is able to rotate with the shaft assy. then suddenly get to something that stops it, that would then cause the rollers in the drum to lock up, mid swing of the lever and cause the sudden jolt/clunk, would it not? Hopefully that is the problem.

[dirty_rat]

I not sure if it would cause the issue you are describing. It is meant to stay stationary, so when it stops, it should act like it was intended, ie. hold the roller holder and allow the kick shaft cams to force the rollers out into contact with the gear. The main issue with it not indexed into its slot would be inconsistent kicker engagement. It might make a clunk noise once engaged, but it shouldn't lock up.
What I'm not sure of is, when loose, as it rotates does it come in contact with any other gears? I don't have an engine apart right now to check, but you might want to spin it around and see if it comes in contact with anything else.
While it didn't happen with your engine, it could also come loose off the roller holder if not indexed into it slot and them move all around in the transmission, causing all kinds of havoc.

[fossilrider]

I am heading down to my shop and will take some pics. It hasn't come off and is where it should be. the slot that it goes in is actually the area between two little cast-in ridges, which means if it spins around, while the lever is being operated, it might eventually come up against the OUTSIDE of one of the ridges, which would act the same way as if it was in the slot except the lever would be near the bottom of the stroke and moving faster. This would cause the rollers to lock up harshly, possibly causing the noise.? I don't know, just surmising. Anyway, I'll send the pics. Thanks for the input.

[viclioce]

If the hold snap is not secure it will spin and strike case areas. That’s probably the metal on metal clunk you’ve been hearing. However it shouldn’t be responsible for start issues or irregular running issues.

Since you have a CDI ignition I would check your flywheel and your CDI unit to make sure the CDI unit is functioning correctly. I don’t know much about the CDI ignitions on these bikes, so someone else should jump in here and address the timing issues. Victor

[fossilrider]

Actually the bike was starting and running great, until this noise started. Once this happened, I quit trying to start it because I was afraid something was going to be damaged. I just got home from my shop where I went over everything inside the engine, again, and saw no damage at all. So, I buttoned it back up and brought it home and am about to put it back in the bike and put the top end on and see what happens. I will post the results.

[dirty_rat]

Inquiring minds want to know...any progress?