Clunk on acceleration or under load

[Firebob462]

Hey all, I'm new to the group. I've been itching to do a go kart project and pulled the trigger last month. It's been fun ( my wife doesn't think so).

I got a old yerf dog 3205 I belive and have done a fair amount of restoration on it. I also did some light motor modifications and electrical work. I just recently finished wiring and some finishing touches.

I've noticed I'm getting a clunky noise that can be felt through the whole kart on acceleration from a stop and if do doughnuts in the dirt parking lot or take a corner right.

I replaced the driven to a 40 series because it had a 30 series driven with a comet 40 drive. I rebuilt the whole jack shaft and replaced the jack shaft sproket(12t) with new chain(40 series). It seems to me that the chain is aligned correctly but I could be wrong. The kart did not do this before with the Frankensteined 40 drive to to 30 series driven, a ****ty chain, a messed up sproket, and a super stretched drive belt.
So I'm left scratching my head.

Is it possible that this could be coming from the torque converter set up? I feel I might have over preloaded the reverse yellow spring on the driven. My gut tells me it's chain related but my knowledge on torque converts is limited. What are the symptoms of a bad drive unit, the comet 40 series drive is the only thing I didn't service or mess with on the whole drive setup.

 

[madprofessor]

The only thing in a 30 or 40 series TC that can make a clunking noise is the flyweights in the driver/clutch, and I doubt that's your issue, it would have done it before also. Betting the ex's share of the 'farm' you're torqueing the chain loose now that there's a driven with a symmetrical belt. (Wondering how that asymmetrical 30 driver worked with a V-belt, or vice versa, whichever.)
Chain may be tight right now, but under load the mount may be flexing, loosening the chain for that moment, and letting it skip teeth with a clunking noise for sure. Stop to check, chain's tight again. Had the same issue for a couple of reasons at once.
First, I went OCD on vibration and used both hard and softer rubber grommets on both sides over/under the motor mounting base, and they compressed under load, making chain skip. Tossed the top ones, better but not enough. Replaced a couple of softer ones underneath so all 4 were hard rubber, made it correct.
Found then that 17" long too-thin motor mounting plate I only supported with 1/2" angle iron on 1 side was flexing down under load, same result. Added angle on other side, got it close but no cigar. Added a cross-brace at 11" mark, finally solved everything. Get the picture? Stuff you can't see while under load unless you had a GoPro aimed at chain/sprockets. Invisible problem when inspected, ghost in the machine.

 

[ONE-EYE]

Hey all, I'm new to the group. I've been itching to do a go kart project and pulled the trigger last month. It's been fun ( my wife doesn't think so).

I got a old yerf dog 3205 I belive and have done a fair amount of restoration on it. I also did some light motor modifications and electrical work. I just recently finished wiring and some finishing touches.

I've noticed I'm getting a clunky noise that can be felt through the whole kart on acceleration from a stop and if do doughnuts in the dirt parking lot or take a corner right.

I replaced the driven to a 40 series because it had a 30 series driven with a comet 40 drive. I rebuilt the whole jack shaft and replaced the jack shaft sproket(12t) with new chain(40 series). It seems to me that the chain is aligned correctly but I could be wrong. The kart did not do this before with the Frankensteined 40 drive to to 30 series driven, a ****ty chain, a messed up sproket, and a super stretched drive belt.
So I'm left scratching my head.

Is it possible that this could be coming from the torque converter set up? I feel I might have over preloaded the reverse yellow spring on the driven. My gut tells me it's chain related but my knowledge on torque converts is limited. What are the symptoms of a bad drive unit, the comet 40 series drive is the only thing I didn't service or mess with on the whole drive setup.

Are you in the bat cave taking that pic? Lol which hole are you using on the driven? Is the chain getting stuck? The #40 chain is slightly thicker than the #41 and #420. Can we get a pic of the back end? Did you have to replace the shaft when going from a 30 series to 40 series? What's the bore size? Did you keep with the 7" driven or switch to a 6"? Did you install a riser kit for clearance?

 

[Denny]

You may get a thumping when the best has to upshift and then quickly down shift and visa- versa on the 40 series.

 

[madprofessor]

You may get a thumping when the best has to upshift and then quickly down shift and visa- versa on the 40 series.

Deny, are you describing a sound from the TC itself, or of the chain snatching during a sudden shift?

 

[Firebob462]

Are you in the bat cave taking that pic? Lol which hole are you using on the driven? Is the chain getting stuck? The #40 chain is slightly thicker than the #41 and #420. Can we get a pic of the back end? Did you have to replace the shaft when going from a 30 series to 40 series? What's the bore size? Did you keep with the 7" driven or switch to a 6"? Did you install a riser kit for clearance?

Middle hole(only hole on my driven). Chain isn't getting stuck. Sounds like a chain skipping to me but wanted everyone's opinion since I now very little about torque converters. I did replace the shaft because the stock one was too short. I kept it with a 5/8 and put new bearings in the jack shaft. I plan on welding a nut on the passenger side but for now I have a couple collars on it. I moved up from a 6 to a 7 driven( China made). I didn't do any sort of riser
Motor sits on a 1/4 steel plate that is welded in almost the entire engine bay area and is just through bolted.

 

[ONE-EYE]

Middle hole(only hole on my driven). Chain isn't getting stuck. Sounds like a chain skipping to me but wanted everyone's opinion since I now very little about torque converters. I did replace the shaft because the stock one was too short. I kept it with a 5/8 and put new bearings in the jack shaft. I plan on welding a nut on the passenger side but for now I have a couple collars on it. I moved up from a 6 to a 7 driven( China made). I didn't do any sort of riser
Motor sits on a 1/4 steel plate that is welded in almost the entire engine bay area and is just through bolted.

I'd prop it up on blocks and run it. Watch both the chain and the belt to see if anything is slipping. It does seem like it'd be the chain but I've also had a driver not work properly and "grab and let go" of the belt. Shook pretty hard off and on. Also check the sprockets and see if there's any new wear and the chain is flowing well. If you're using #40 chain, try running with #420. It should be easier to at least see where the sound is coming from with it on blocks jacked up.

 

[Denny]

The shock vibration is from the clutches and belt not being able to react fast enough to the changes from the extreme moves.

 

[Karttekk]

I'd say part of the problem is the worn driven sprocket on the axle. The teeth are pointy which means they're worn out. Replace it and see what happens. It needs replaced regardless if it fixes the clunk or not but I'm thinking it will. The new chain isn't getting along with the worn sprocket.

 

[Firebob462]

I will definitely put the kart on blocks tonight when I get off work and check to see whats happening,although I'm not sure it will help since it seems to only happen under load. How tight does the chain need to be? Any differences I should be looking for or listening for to distinguish if it's the chain or torque converter besides the obvious ones? When you where having those issues with the drive what did it sound like and what where the symptoms. The drive unit on this set up is an old comet and I'm sure it could benefit from being rebuilt/cleaned and restored. I would have done it already but it looks like I needed to weld up a special tool to pull the drive unit apart from the videos on YouTube so I put the idea on the back burner.

 

[Firebob462]

I'd say part of the problem is the worn driven sprocket on the axle. The teeth are pointy which means they're worn out. Replace it and see what happens. It needs replaced regardless if it fixes the clunk or not but I'm thinking it will. The new chain isn't getting along with the worn sprocket.

I was kinda thinking the same thing but wanted to be a cheap *** lol. I think I'll pull the trigger on a new sproket. Should I buy a sprocket hub and a new sprocket or should I go with the yerf dog replacement that has the hub built in?

 

[ONE-EYE]

I will definitely put the kart on blocks tonight when I get off work and check to see whats happening,although I'm not sure it will help since it seems to only happen under load. How tight does the chain need to be? Any differences I should be looking for or listening for to distinguish if it's the chain or torque converter besides the obvious ones? When you where having those issues with the drive what did it sound like and what where the symptoms. The drive unit on this set up is an old comet and I'm sure it could benefit from being rebuilt/cleaned and restored. I would have done it already but it looks like I needed to weld up a special tool to pull the drive unit apart from the videos on YouTube so I put the idea on the back burner.

If either are slipping, you could sometimes see it. If either of the pullies are dirty, have rust spots, or springs inside aren't functioning properly, it won't engage or disengage properly. Mine had been sitting for 15yrs untouched so I knew I'd need to replace anyway. Check the wear on the belt for uneven wear. It could be slight or extreme but if you replace, only use a comet belt! Don't try to save money here. I haven't seen anyone needing a welder to pull a driver apart personally. They normally come apart in 2 pieces with the springs inside one piece. Is it rusted possibly? Here's what I was talking about the belt...

 

[madprofessor]

Should I buy a sprocket hub and a new sprocket

I'm a big proponent of sprocket carrier hubs with split sprockets, instead of plain sprockets where you have to R&R everything on the axle to change one. Just get a hub with a 5.25" bolt circle and be done with it, an R&R one time to put it on, and just $15 split sprocket changes in 5 minutes from then on, for different ratios, worn out sprockets, etc. ............... Here's probably the cheapest hub...........
Unihub - Sprocket Hub | AZ2556 | Azusa 2556 | BMI Karts And Parts ..............and here's one similar to what I have .................
Heavy Duty Aluminum Sprocket Hub (1" Bore) - Black | 433968 | BMI Karts And Parts ..............and split sprockets of any size you want..............
#35 Split Sprocket | 6335** | BMI Karts And Parts

 

[madprofessor]

worn driven sprocket on the axle. The teeth are pointy which means they're worn out.

The teeth of the axle sprocket are indeed pointy, and the sprocket may be worn, but it doesn't look worn enough to cause the chain to skip. More often than not, the teeth of a worn sprocket will be shortened and dull, or even folded over in the direction of chain travel.
Speaking of chain travel direction................That master link's clip is on backwards. Always have the open end of a master link clip trailing behind the direction of travel of the chain, the closed end needs to contact the next sprocket or roller first.

 

[Karttekk]

Replace the sprocket regardless, it's shot. Funny no one noticed that.

 

[Karttekk]

Taking everything off to access it is no big deal. Get what sprocket shipped with the kart originally, less chance of something going wrong in the process. Just my opinion after restoring close to 20 karts.

 

[Firebob462]

Taking everything off to access it is no big deal. Get what sprocket shipped with the kart originally, less chance of something going wrong in the process. Just my opinion after restoring close to 20 karts.

That's kinda what I was thinking. How tight should the chain be? Do they make any good bolt on chain tensioners for when these chains stretch?

 

[Firebob462]

Speaking of chain travel direction................That master link's clip is on backwards. Always have the open end of a master link clip trailing behind the direction of travel of the chain, the closed end needs to contact the next sprocket or roller first.

Thanks for pointing that out

 

[Karttekk]

The chain should have a slight "droop" in it or roughly a 1/2" to 3/8" or so of flex. Too tight and it could bind and pop, too loose and it will skip over the teeth. Use your judgement. You'll be able to tell if it's right when you ride it.

 

[Firebob462]

I'm a big proponent of sprocket carrier hubs with split sprockets, instead of plain sprockets where you have to R&R everything on the axle to change one. Just get a hub with a 5.25" bolt circle and be done with it, an R&R one time to put it on, and just $15 split sprocket changes in 5 minutes from then on, for different ratios, worn out sprockets, etc. ............... Here's probably the cheapest hub...........
Unihub - Sprocket Hub | AZ2556 | Azusa 2556 | BMI Karts And Parts ..............and here's one similar to what I have .................
Heavy Duty Aluminum Sprocket Hub (1" Bore) - Black | 433968 | BMI Karts And Parts ..............and split sprockets of any size you want..............
#35 Split Sprocket | 6335** | BMI Karts And Parts

I love the idea of this I'm defiantly going to be thinking about it as a potential option.