Repower crankshaft.. pulley distance question

[FLtractor 243]

Afternoon,

 

Have interesting question I’ve attempted to look online to see if forumla to equal and solve such as distance height ect such as an engineer or math aficionado would think in terms of.. which I am neither… 856.. K181. Distance base to middle crankshaft pulley is 4.75 inches… 

if used predator 301cc 8HP.. distance base to middle crankshaft 5.2 inches plus 0.5 for predator engine mount.. puts it at 5.7 which is 0.95 higher than stock pulley crankshaft location.. is there place to slide engine farther or back to accommodate for this change.. therefore allowing keeping the orignal belt.. belt guard without modification of fingers top and bottom to hold belt when depress clutch? 

[ri702bill 13,231]

You are correct that you DO need A belt guard for correct clutch action - the belt MUST come to a complete standstill in order to shift the Unidrive. Will it be the original WH one - maybe and maybe not....

If going with the HFT Predator, get the replacement warranty to gain a second chance to fix the spacing if your math is off...

[FLtractor 243]

1 hour ago, ri702bill said:

You are correct that you DO need A belt guard for correct clutch action - the belt MUST come to a complete standstill in order to shift the Unidrive. Will it be the original WH one - maybe and maybe not....

If going with the HFT Predator, get the replacement warranty to gain a second chance to fix the spacing if your math is off...

As far as spacing .. since the crankshaft of 301cc predator would be 5.7 inch roughly

instead of 4.75 orignal - is there anyway to know how far to move crankshaft to make up for this difference besides trial and error? If I moved the crankshaft- engine 1 inch back to accommodate for the 1 inch above original crankshaft pulley location- wonder if i could just get a belt that’s 1 inch longer .. keeping everything else the same 

Edited 11 hours ago by FLtractor

[Ed Kennell 47,666]

I would position the engine to get the best fit with the existing belt guard to minimize the amount of altering you will need to do to make it fit and work.   

Then buy the correct belt length.

[ri702bill 13,231]

13 minutes ago, Ed Kennell said:

Then buy the correct belt length.

Good point. When I put the 8 speed in my 854, I had to go to a 1" shorter belt (69" vs the OE 70") Due to having to change the Unidrive input pulley diameter. ...

As I recall the HFT engine needs an adapter under it to boly to the frame - that may be the key piece here...

[8ntruck 9,356]

Pulley diameters come into the equation as well. 

 

If you keep the same pulley diameters, the amount of the engine set back becomes a trig problem.  To solve that, you will need to know the original horizontal and vertical distanced between the crank center and the tranny input shaft center.

 

Keeping the same pulley diameters and drive belt means that the direct distance between the crank and input shaft should remain the same. Increasing the vertical distance by an inch will require reducing the horizontal distance by a fraction of an inch - i'm going to gustimate that distance will be somewhere between 1/4 and 1/2 inch.

 

Now, when you throw the clutch into the calculations, the above basically gives you a starting point, as the kinimatics of a belt and 3 pulleys is different than a belt and 2 pullies.

[FLtractor 243]

4 hours ago, Ed Kennell said:

I would position the engine to get the best fit with the existing belt guard to minimize the amount of altering you will need to do to make it fit and work.   

Then buy the correct belt length.

Great point Ed. Thank you

[wallfish 20,699]

I agree with Ed. Set the engine and everything else the way you want it and measure for the correct belt. The clutch idler pulley will allow for some tolerance in belt length. Slotting the engine mount holes can also allow for some adjustment. If you NEED to keep the original belt, put it on, then mount the engine. ie: drill new holes

[FLtractor 243]

4 hours ago, ri702bill said:

Good point. When I put the 8 speed in my 854, I had to go to a 1" shorter belt (69" vs the OE 70") Due to having to change the Unidrive input pulley diameter. ...

As I recall the HFT engine needs an adapter under it to boly to the frame - that may be the key piece here...

The adapter is 0.5 inches tall.. the great feature of them being made for predator engines is they have enough pre drilled hole width and length with enough play to slide the engine as needed after bolting it to tractor frame. 

[FLtractor 243]

33 minutes ago, 8ntruck said:

Pulley diameters come into the equation as well. 

 

If you keep the same pulley diameters, the amount of the engine set back becomes a trig problem.  To solve that, you will need to know the original horizontal and vertical distanced between the crank center and the tranny input shaft center.

 

Keeping the same pulley diameters and drive belt means that the direct distance between the crank and input shaft should remain the same. Increasing the vertical distance by an inch will require reducing the horizontal distance by a fraction of an inch - i'm going to gustimate that distance will be somewhere between 1/4 and 1/2 inch.

 

Now, when you throw the clutch into the calculations, the above basically gives you a starting point, as the kinimatics of a belt and 3 pulleys is different than a belt and 2 pullies.

This is the math part i understand how to calculate.. thank you for teaching me

pulley diameter matters just as much

[FLtractor 243]

1 minute ago, wallfish said:

I agree with Ed. Set the engine and everything else the way you want it and measure for the correct belt. The clutch idler pulley will allow for some tolerance in belt length. Slotting the engine mount holes can also allow for some adjustment. If you NEED to keep the original belt, put it on, then mount the engine. ie: drill new holes

Good to know the clutch allows for tolerance slack movement. The predator mount would help with the engine setting. Thank you 

[FLtractor 243]

It seems that it would be much less hassle

to just buy that K161 tiller engine I posted about for $75.00 and take the recoil

parts off.. just bolt it directly onto my K181 that’s on my 856… would be much easier quicker than predator swap. If that is indeed as simple as unbolting the recoil pull start… cup and if needed bearing plate swap and if that is all worth $75 to do that swap

to  simple recoil would there be cheaper brand new modern recoil parts I could buy and just bolt on.. maybe from newer Kohler or even a non Kohler modern easy to obtain exact parts?

 

Edited 5 hours ago by FLtractor

[702854boy 1,164]

Why not just take a couple of days and work slowly with the guys on here and get the original k181 running? If I remember correctly from previous posts, it doesn't need much more than just being rewired and all of the grounds cleaned up.

[kpinnc 19,017]

Hard to beat an old Kohler, and a recoil start might be nice when battery and starter maintenance is concerned. 

 

But if you go with a repower, most newer engines are more compact and the PTO as a result is lower, and the engines tend to be more narrow as well. 

 

I've repowered 3 machines with Vanguard V twins. That means not only raising the engine by about an inch, but shifting it to the right as well. The only way I could find that works consistently is to fab up an adapter the bolts to the existing frame holes while providing a new bolt pattern to interface with the smaller engine pattern. 

 

One thing that helped get my builds in the ballpark was to use the PTO hoop lower bracket and the beltguard as a guide for where the PTO shaft needs to be. It isn't perfect but it helps alot. It at least removes guesswork from the equation. 

 

Just don't swap any PTO brackets. Different models did use different locations as well as manual and hydros are different. Stick with what was originally on your machine. One pic below shows how different the locations can be between models. 

 

 

 

 

 

Edited 3 hours ago by kpinnc