How many coils MAX on clutch spring to cut?

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greasemonkey060

New Member
#1
#1
Newbie here. I just picked up a db30 a few days ago. Way underpowered for my weight (240 lbs) but what can I expect for a big guy? Blah blah 6.5 clone swap yeah yeah.

After doing searches on how to do it (so I wouldn't get flamed! Haha), I cut down the clutch spring and re-assembled it. I think I cut 4 or 5 off, definitely enough to make it a pain in the :censure: to get back on, but I used the hose clamp tip (thanks, btw) and I muscled it on.

I test rode it, and I noticed little improvement in a higher stall. But I was thinking about cutting more, my question:

How many coils can I cut before I start weakening the spring rate to work properly (lowering stall rpm)? Or how many before it's impossible to get back on?



I've got a 3.5 Robin motor laying around, I might throw it in since I don't have the $$$ for a 6.5 or something better. So no need suggesting a motor swap QUITE yet.

THANKS!
 
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greasemonkey060

New Member
#5
#5
vette66_00 said:
Put the 3.5 on. Same clutch and same mounting. The stock motor is crap for power a 3.5 would be night and day on that mini.
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Oh no! You my friend gave me something to do today! Thanks!


I never got around to measure the output shaft or mounting holes to see how easy the swap would be, but now I know that they're the same...


Thanks everyone!
 
vette66_00

vette66_00

Active Member
#6
#6
The only difference from the 2.8 and the 3.5 is the output shaft. One is metric and one is standard as far as size goes. It a very small amount the larger of the 2 would be the 2.8 shaft. My 2.8 clutch went on a 3.5 briggs without a probelm. It felt a bit loose but works good. The block mounting holes lined right up on my edger when I took a 3hp off and put the 2.8 on.
 
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G

greasemonkey060

New Member
#8
#8
Quick update on my progress.


I spent (too much) time yesterday afternoon trying to get the pulley/clutch assembly on the 3.5 I had. Key stock is f:censure:ed.

Yeah I used a three jaw puller, and yes I pulled all the snap rings out. It's just seized and rusted on. And I don't have a torch handy to help the process.

Did a want ad on Craigslist for a small engine, had a few replies so I might be doing a 5+hp swap sooner than I thought!
 
vette66_00

vette66_00

Active Member
#9
#9
If you do anything 5hp and up you are going to need a new clutch. The old one is 5/8" the 5hp and up to 7hp is 3/4" above 7hp they go to 1". This is for the out put shaft size. Also above a 3.5hp engine the block holes change also requiring you to re-drill holes for mounting.
 
oldyeller

oldyeller

New Member
#11
#11
Getting back to the clutch spring idea..Has anyone tried drilling the shoes to lighten them instead of or along with cutting the spring?..We used to race small 90cc two stroke atvs and this was a very common practice to raise the engagement speed after doing some engine mods..
 
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greasemonkey060

New Member
#12
#12
oldyeller said:
Getting back to the clutch spring idea..Has anyone tried drilling the shoes to lighten them instead of or along with cutting the spring?..We used to race small 90cc two stroke atvs and this was a very common practice to raise the engagement speed after doing some engine mods..
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Interesting! So does that just make the clutch slip a alittle bit therefore, higher stall? Would that ruin clutch life?


What about a drilled clutch bell? What would that do to affect the stall? Similar to a drilled flywheel like http://http://partssearch.off-road.com/productDetail.php?pid=1208298?
 
oldyeller

oldyeller

New Member
#13
#13
greasemonkey060 said:
Interesting! So does that just make the clutch slip a alittle bit therefore, higher stall? Would that ruin clutch life?


What about a drilled clutch bell? What would that do to affect the stall? Similar to a drilled flywheel like http://http://partssearch.off-road.com/productDetail.php?pid=1208298?
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The whole basis on how the clutch works is centrifugal force..When the rpms get high enough the shoes of the clutch are forced out against the bell and the clutch engages...The only way to raise the engagement point is to install a stiffer spring or make the shoes lighter..It may shorten the life of the shoes a little with a higher engagement speed but I'm not sure how much....Drilling the bell would have no effect on engagement speed since it is on the outside half of the clutch..Making the bell lighter by drilling it should in theory help the engine rev a little quicker by being lighter but I'm not sure you could remove enough wieght to make much of a difference..
 
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greasemonkey060

New Member
#14
#14
oldyeller said:
The whole basis on how the clutch works is centrifugal force..When the rpms get high enough the shoes of the clutch are forced out against the bell and the clutch engages...The only way to raise the engagement point is to install a stiffer spring or make the shoes lighter..It may shorten the life of the shoes a little with a higher engagement speed but I'm not sure how much....Drilling the bell would have no effect on engagement speed since it is on the outside half of the clutch..Making the bell lighter by drilling it should in theory help the engine rev a little quicker by being lighter but I'm not sure you could remove enough wieght to make much of a difference..
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Ah. Yeah I was just thinking about the idea. Sounds like something to play around with if you've got an extra clutch and an afternoon to tinker.
 
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