Full Suspension Big Block Mini-Buggy Build

[SquidBonez]

Been doing some test riding before I finally paint it to make sure there's no welding left to do. After throwing a chain I decided to add a storage bin to the side to bring extra chain/masterlinks/tools with me in case of a breakdown. But the biggest addition is a spring loaded adjustable chain tensioner.


Not only do I have the slots in the engine plate for adjustment, I now have this spring loaded tensioner to actively tighten the chain as it wears. The tensioner itself also has multiple spring/idler wheel positions to allow for different spring strengths/sprocket sizes. Obviously you still need to keep an eye on you chain, but this at least will take up the slack that happens between adjustments. Hopefully this prevents any future chain-related issues. And if not, I have my storage bin to hold my tools to make any on-the-go repairs.

 

[Master Hack]

That will help a lot. What is the blue material? I made one outta 90D polyurethane, but it wore out quickly. Then i switched to an idler sprocket. End of problem. Don’t underestimate the required spring tension.

 

[SquidBonez]

That will help a lot. What is the blue material? I made one outta 90D polyurethane, but it wore out quickly. Then i switched to an idler sprocket. End of problem. Don’t underestimate the required spring tension.

Some sort of high density plastic. Got it off Amazon. As for the spring tension I believe it will be enough, but if not i have multiple holes to allow for different size/length/strength springs. Gonna try this one first because I had it on hand.

 

[Master Hack]

Since l'm a cheap scrounger, l used a spring from the neighbors old trampoline. It took 3 tries to settle on the right tension.

 

[lug-nuts]

The spring from a cheap wood clamp works good too, and theyre only a couple bucks for clamp.

 

[lug-nuts]

The spring from a cheap wood clamp works good too, and theyre only a couple bucks for clamp.

inside pic showing
the spring

 

[SquidBonez]

Just working out the kinks before paint. Also got this set of tires (square setup rather than staggered). 19x7-8 all the way around. This allows me to rotate my tires and also gives a more neutral handling/eliminate understeer. Haven't tried them out yet but these tires will be better on the trail. Also they are a lot lighter than the old rear tires so they should free up a bit of power.

 

[SquidBonez]

Been having big issues with chain tension. The spring loaded tensioner seems to actually exacerbate the problem rather than help, so I've ditched it (still holding on to it in case it becomes useful later). I thought I may have had my chain set too tight, but that doesn't seem to be the issue.

The chain I'm using is D.I.D. #420 gold chain, but I'm thinking I need to go bigger. I could go to #428 chain, but I think I'm going to jump up to #530 motorcycle chain for extra peace of mind. I'd rather overdo it than underdo it. I may have to space out my pulleys to fit the larger sprocket, but it seems like it might work. While #530 sprockets are hard to find for go-kart applications, #50 industrial chain sprockets are the same exact size as #530 and are relatively common. Downside is now I have to remove my axle to do gearing swaps (had a split sprocket before) and I am back to relying on manual chain tensioning.

Now just waiting on parts...hopefully this fixes it. Has anyone else had issues with chain stretch with big block engines?

 

[Master Hack]

Yep, had problems with #420 chain. Switched to #40H and solved that problem.
40H is substantaly stronger than 420. Same pitch so sprockets don't need changing.

 

[SquidBonez]

Yep, had problems with #420 chain. Switched to #40H and solved that problem.
40H is substantaly stronger than 420. Same pitch so sprockets don't need changing.

#40 chain will fit pitch wise, but doesn't it have tons of side to side slack as it's wider than #420? Also apparently this D.I.D. gold chain has a higher tensile strength (4930lbs) than the #40H I could find (just above 4000lbs on average). Do you know where to find strong 40H chain?

 

[Master Hack]

40 is a little wider, but not a lot. Doubtful you could tell the difference at a quick glance.
l don't remember all the detail BS cuz i'm old and did this yesterday....
l had similar problems and talked to these guys and end of problem.
don't know if the difference is USA chain vs foreign, 40 vs 420 or what.

Premium Roller Chain, Engineering Chain & Sprockets - Nitro Chain

www.nitrochain.com

 

[Denny]

40 is a little wider, but not a lot. Doubtful you could tell the difference at a quick glance.
l don't remember all the detail BS cuz i'm old and did this yesterday....
l had similar problems and talked to these guys and end of problem.
don't know if the difference is USA chain vs foreign, 40 vs 420 or what.

Premium Roller Chain, Engineering Chain & Sprockets - Nitro Chain

www.nitrochain.com

Are you jerking our chains, man?

I’ve waited years for the right time to use that!

 

[Master Hack]

I set ya up! Yer welcome.

 

[TNThomas]

I think your chain tensioner should be mounted such that it applies tension on the top chain, not the bottom. The bottom chain should naturally have most of the slop picked up from the tension force of the jackshaft sprocket pulling on it. It's the top section that's just flopping around since it's essentially being "pushed" by the jacksfaft sprocket. One idea would be to mount some sort of bolt with a wheel on it in-between the links. That way you could fine tune the tension via threading in/out the bolt.

Check these folks out, tons of size options for chains/sprockets, this is who I went with.

Premium Roller Chain, Engineering Chain & Sprockets - Nitro Chain

www.nitrochain.com

 

[SquidBonez]

#530 chain is going in. For a reference, this is the size difference between #420 and #530:

If it's good enough for 1000cc sports bikes then it's gotta be good enough for a 440cc Duromax. These are #50 chain industrial sprockets but they fit perfect. Heavy as all hell though. At least they're less likely to bend if I hit something. I was originally running a 5.4:1 final ratio with the #420 and now I'm running a 5:1. Not a huge change but should gain a bit of top end.

 

[SquidBonez]

Well after installing #530 chain and sprockets I found the next weak point: jackshaft bearings. I wasn't sure if it was the bearings themselves or the backplate I made/modified but I just broke down and bought a pre-made jackshaft kit and swapped my pulleys over.
I had to modify it slightly of course. Made some clearance cuts for the exhaust and the frame. Plus I had to make new spacers out of 3/4" gas pipe to get the pulleys to line up as the #420 sprocket that comes with this kit is a different width than the #530 sprocket I installed.


After taking it for a rip around the yard everything still seems as I left it. No chain stretch and no destroyed bearings. I'd call that a success. It's now ready for it's first true maiden voyage (after an oil change for good measure).

Another concern I had was the axle sprocket size itself. Stepping up to a larger chain means larger diameter sprockets, which in turn means less ground clearance. I decided to go with a 50 tooth axle sprocket (previous was a 54 tooth) as to not make it too much larger. Even with the longer gearing and knobby tires it still kicks out the back end on dirt and can do donuts on pavement. Ground clearance is 3-1/4"...that has me less pleased, but nothing I can really do about that.

Final thoughts: my next buggy is getting a custom jackshaft rather than a backplate-type system. This would have solved a lot of my issues. My eventual plan is to have an electric-powered buggy as well, so a jackshaft system would also make that conversion easier as well as allow me to reduce the axle sprocket size.

 

[Master Hack]

Thats a nice upgrade. Chain stretching is a serious PITA!
Let us know how it holds up!
keep a close watch on where that CVT plate bolts to the engine. I just fixed BIG problems caused by them bolts shearing. It got ugly!

 

[SquidBonez]

Finally got the buggy out for it's first real test. I did wide open fields and some bump trails. Going from a solid frame go kart to this is night and day. The suspension is very soft and absorbs bumps that would rattle my teeth out before like it's nothing. It also handles small jumps very well. The brakes are also way better than the old kart. I can lock even these knobby tires up no problem.

Seeing as this test was to find weak points, I'm pleased to say there's nothing major as of right now. The header pipe rattled itself loose, so I'm going to make a brace for it that mounts to the engine block. The belt also sqeals, but I think I just need to adjust the belt alignment. The chain didn't seem to stretch at all, which is promising. The engine did stall once, but I think that's just because I hit a big bump. It started right up after with no issues. The engine does "break up" a little if you're going fast over rough terrain, but that's probably a side effect of the swingarm-mounted engine design. Anybody else with this setup experience this issue? I know most gy6 buggies are set up this way.

 

[SquidBonez]

Got a brace for the exhaust fabbed up, and I've got a tachometer now.


I've also figured out the belt squealing issue. At first I thought it was an issue with pulley spacing, but nothing I did helped. These Chinese manufactured belts actually run small. The chinese belts that came with this torque converter kit are labeled as 203785 size. Luckily I have original Comet brand 203785 belts. I put both side by side and the Comet belt is actually noticeably longer despite being the same size number. Swapped out the Chinese belt for the Comet and that fixed my issue. No more squealing. If you don't feel like paying the extra money for an OG Comet belt (they're just under $40 a piece), go the next size up (203786) and buy a Chinese belt. I'm willing to bet that it would actually work better than the belt that comes with these kits since they run too small.

 

[Denny]

Chineseum belts suck! Genuine Comet belts only!!!!!!