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Author Topic: STIHL HT-KM Pole pruner  (Read 3004 times)

Offline Mick

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STIHL HT-KM Pole pruner
« on: January 31, 2018, 10:03:47 PM »
STIHL HT-KM Pole pruner - KombiTool


Had a customer bring one of these combi tools in for repair this week.  It stopped oiling, and the customer had had it to pieces, fitted a new pump but still couldn't get it to oil, plus it had now developed a oil leak. (see if you can spot the mistake). 

Some pics, just in case your curious what's inside one of these units. also notice the lack of grease, not bad for a unit which is a month old, eh.








And as for the oil leak, see if you can spot the mistake,  You can see the oil pump, visible in both of these pics.

Wrong Pump.


Right Pump.



Offline RusticRatbag

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Re: STIHL HT-KM Pole pruner
« Reply #1 on: April 22, 2018, 05:43:26 PM »
I dropped a large branch on my HT-KM a few weeks ago and smashed the casting where the pole drive goes in. I was thinking about getting two new halves and rebuilding it, it’s only five years old and hasn’t done a lot of work, but funked it and bought a new complete unit last week. I wish I hadn’t, the build quality of the new one seems very poor. Diecast alloy is always brittle, but the new one is half as stout as the original, it all looks a bit flimsy. Made in China perhaps? The original doesn’t look a difficult job to take apart and rebuild, are there any things to watch out for if the situation crops up again....?

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #2 on: April 22, 2018, 06:28:49 PM »
I dropped a large branch on my HT-KM a few weeks ago and smashed the casting where the pole drive goes in. I was thinking about getting two new halves and rebuilding it, it’s only five years old and hasn’t done a lot of work, but funked it and bought a new complete unit last week. I wish I hadn’t, the build quality of the new one seems very poor. Diecast alloy is always brittle, but the new one is half as stout as the original, it all looks a bit flimsy. Made in China perhaps? The original doesn’t look a difficult job to take apart and rebuild, are there any things to watch out for if the situation crops up again....?

Hi, and welcome to TGMF.

I take it you broke the lower casting on your HT-KM  ?  If not and it's only the top half it's a really quick and easy job.  If it's the lower one then it's a bit more involved, but not that difficult really.  Providing you can obtain the right parts, there's a couple of variants of the older pruner. 

As for the latest models, yes they don't look very impressive, and almost look like they're designed for cordless (battery powered) machines. 

Offline RusticRatbag

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Re: STIHL HT-KM Pole pruner
« Reply #3 on: April 23, 2018, 04:48:01 PM »
Both halves! And the drive pole bent at a racy angle......
Yes I can see the top half only would be straightforward but I guess getting the bearings out of the other half wouldn’t be too difficult. I think I found that both halves came to about £100 so with seals etc it would be about two thirds the cost of the new one. But would make a better machine. Well I’ll see how long the new one lasts.....
Many thanks

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #4 on: April 23, 2018, 05:23:45 PM »
Both halves! And the drive pole bent at a racy angle......
Yes I can see the top half only would be straightforward but I guess getting the bearings out of the other half wouldn’t be too difficult. I think I found that both halves came to about £100 so with seals etc it would be about two thirds the cost of the new one. But would make a better machine. Well I’ll see how long the new one lasts.....
Many thanks

Aha, both bits, that was unlucky.  Well it's pretty straight forward to dismantle once you get the sprocket screw undone, after that it's a simple case of removing the top casing and lifting out the two shafts complete with bearings.  You will also need to extract the oil pump and push it back into the new housing.  You can use a m5 screw and a Nyloc nut wound into the end of the pump to gauge the depth, and to extract it and tap it back in with.  ;)

Let us know how it goes.   :)

Offline Homer

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Re: STIHL HT-KM Pole pruner
« Reply #5 on: October 26, 2018, 03:52:03 AM »
Hi Mick:
I have a couple questions about this HT-KM so it's great to finally find someone familiar with the oil pump.
I'm not sure about the answers to the puzzle from the first post but we can get to that later.  :)

My problem is with the bar oil consumption as stated in the manual.  It says a tank of oil will only last for half a tank of fuel.  My unit (purch. new and still very few hours on it) is the reverse, it goes through about half a tank of oil per tank of fuel.
I contacted them and told them there must be a typo, thinking of the warranty nightmare of a design that runs out of oil before fuel. 
They told me no typo, and that I should take my new unit in for service.  The auth. service station said they replaced the oil pump.  Now it behaves exactly as before.
Do you recall how much oil these chains get?  Is it visibly obvious?
               Thanks

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #6 on: October 26, 2018, 05:27:32 PM »
Hi Mick:
I have a couple questions about this HT-KM so it's great to finally find someone familiar with the oil pump.
I'm not sure about the answers to the puzzle from the first post but we can get to that later.  :)

My problem is with the bar oil consumption as stated in the manual.  It says a tank of oil will only last for half a tank of fuel.  My unit (purch. new and still very few hours on it) is the reverse, it goes through about half a tank of oil per tank of fuel.
I contacted them and told them there must be a typo, thinking of the warranty nightmare of a design that runs out of oil before fuel. 
They told me no typo, and that I should take my new unit in for service.  The auth. service station said they replaced the oil pump.  Now it behaves exactly as before.
Do you recall how much oil these chains get?  Is it visibly obvious?
               Thanks

Hi Homer, and welcome to TGMF

To be honest it will depend on what Combi engine unit you're running this attachment on.  The fuel tanks and consumption vary quite a bit.   Do they state that figure based on what engine used?

Current combi engines
KM 56 RC-E = Tank volume  0.34
KM 94 R-CE = Tank volume  0.54
KM 111 R    = Tank volume  0.71 
KM 131       = Tank volume  0.71
KM 131 R    = Tank volume  0.71 

I can't see how they can state the oil usage when there's different engine units being used, some have massive fuel tanks, some have tiny tanks.   If it's a domestic engine unit I'd say top up the chain oil every couple of tanks of fuel.     
« Last Edit: October 26, 2018, 06:53:48 PM by Mick »

Offline Homer

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Re: STIHL HT-KM Pole pruner
« Reply #7 on: October 30, 2018, 03:23:48 AM »
Well that makes too much sense Mick. :D
I can see that would make a big difference with that kind of variation in fuel tank size.
Turns out they use the same blurb in all their pole saw manuals about the oil tank only lasting for half a fuel tank.
Here's a guy verifying that to be correct for his HT-130, which has .22 l oil tank (seems the standard for the pole pruners) and .53 l fuel tank.
https://www.arboristsite.com/community/threads/pole-prunner-using-too-much-oil.311550/
My combi engine is the 56, so smaller fuel tank and the oil should last more than 1/2 tank of fuel.

So I pulled my oil pump out and re-aligned it.  It's much different from the one you show at the top of the page.  The pump press fits into aluminum housing with no rubber lines.  You can see it here (#2), maybe yours was an older style?  http://visionspares.com/getdiagram/b2eb2d45-5435-4219-a7d2-fdc3f63242d0.gif

Anyway, it is definitely delivering more oil now, will have to see how soon it uses a tank of oil as I haven't had a chance to do any cutting yet.

The unfortunate part is this means the dealer may have done nothing where they said they changed the pump.  To top it off, they tried to charge me for it while the unit was still under warranty.  The most generous I can see is that they did replace it, but aligned it incorrectly as the original had been?  And then did not measure the oil usage?
Anyway, I'd put it down to a dealer problem but I had also reached out to the Canadian distributor as well as Germany (head office).  So I'm probably done with the brand as far as any other new products.

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #8 on: October 30, 2018, 09:48:11 PM »

So I pulled my oil pump out and re-aligned it.  It's much different from the one you show at the top of the page.  The pump press fits into aluminum housing with no rubber lines.  You can see it here (#2), maybe yours was an older style?  http://visionspares.com/getdiagram/b2eb2d45-5435-4219-a7d2-fdc3f63242d0.gif


Homer,  Actually the one you have in that parts diagram is the old version, the one I have in my images is the latest version.  ;) https://www.stihl.co.uk/STIHL-Products/KombiSystem-and-MultiSystem/KombiTools/274713-1482/HT-KM.aspx

As for your dealer doing the repair, why did they throw the warranty out? did they say you had caused the failure, as in using the wrong oil, or perhaps getting dirt or sawdust in the tank?  If they hadn't aligned the pump properly that can cause the flow to be restricted, hence why there is a direction diagram moulded into the aluminium casing, near to where you insert the pump.   

Glad you have it oiling now though.  8)

Offline Homer

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Re: STIHL HT-KM Pole pruner
« Reply #9 on: November 02, 2018, 02:36:56 AM »
They weren't trying to void the warranty, they just didn't want to honour the 2014 2yr extended warranty.  It was just over a year old and they were trying to tell me the 2yr didn't apply to the attachment even when I showed them the printout. :D  I told them to call me if they couldn't get the claim covered and never heard back from them.
This housing doesn't have any diagram in it to show alignment.  Maybe they added that later due to problems?  If they've re-designed like in your images at the top of page, I would think the design was problematic.
As I mentioned, either they did not actually change the pump, or they did but aligned it the same way the original had been (wrong).  That is the only way I can see that the unit behaved exactly the same before and after the dealer service.  Some testing would have shown them this, but I don't think they did any before or after.
But this was not my first struggle with this unit.  Previous to the pruner attachment issue, the combi engine fuel cap seized.  This recall was the problem:
https://www.stihlusa.com/information/recalls/toolless-fuel-cap/
I had to pay for a new cap as the Canadian dist. said it was a US only problem (like we don't have ethanol in the fuel here ;) ).
Sorry if it seems like I'm bashing the brand or dealer, I work in service in a different field and am pretty understanding of the concerns.  However, I also realize sometimes you have to take some losses to keep the customer happy.  I'm not hard to please. :)
« Last Edit: November 02, 2018, 02:45:22 AM by Homer »

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #10 on: November 02, 2018, 08:48:13 AM »
Those fuel caps are a nightmare at best to be fair, not one of their better moves.  They are usually tethered in such a way that when refilling with oil the inner part of the cap lays on the body of the saw which is covered in crap. then you transfer it inside the tank when refitting. lol..  Seen this a lot even on pro chainsaws.   We only run %5 ethanol here in the UK, and to be honest that causes more trouble than enough.   This will push ore people to battery powered products.

The pump fitting diagram might not be present on your model, as it's for a different country to ours, but I'll see if I can find one and take a photo for reference.   ;)

The dealer should have tested it after repair though, I'd be really surprised if they didn't.   

Offline Homer

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Re: STIHL HT-KM Pole pruner
« Reply #11 on: November 04, 2018, 01:51:07 AM »
It's possible they tested it, but only to see if oil was coming out, which it already was when I took it in.  But the complaint was that it was not oiling enough, so some kind of volume check needed to be done and it could not have been delivering the adequate amount.
Maybe there is no spec available for them to check.  I really don't know how the situation should have been handled.  I do know I would have probably overheated and damaged bar and chain if I'd used it much when new or after the dealer serviced it.

Now are you going to spill the beans as to the puzzle at the top of the page? :D  Not having seen the new style pump I'm at a loss as to what was wrong there.

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #12 on: November 04, 2018, 09:45:33 AM »

Now are you going to spill the beans as to the puzzle at the top of the page? :D  Not having seen the new style pump I'm at a loss as to what was wrong there.


Well on the new type head the pump is exposed permanently as you can see from the two pump pics above. 

The pic with the wrong pump:  So in this image if you look closely you'll notice the pump fitted has a groove / channel down the side of it.  Its the older style pump which needs this groove to supply the oil to it, but fitted to this latest unit all it will get is fresh air.  You have this style pump in your unit, the oil is fed through the bottom of it via that channel.

The second pic: This has the correct pump fitted which doesn't have that groove / channel.  And is fed from each side via the rubber pipes.

Basically, new unit has a different pump with just a hole each side.  Older style has channel up the side, and one hole, same as in your own unit.

Offline Homer

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Re: STIHL HT-KM Pole pruner
« Reply #13 on: November 05, 2018, 02:53:02 AM »
So that would also explain the oil leak, right down the slot.

I had been wondering why I was seeing entire gearheads new for as low as $60 ($20 for chinese knock-offs), pretty decent price if you are going to spend $20 on an oil pump anyway.  Now I realize these are 'old-style' gearheads, so maybe not such a bargain.
Learned lots from this thread.  :)

Offline Mick

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Re: STIHL HT-KM Pole pruner
« Reply #14 on: November 05, 2018, 07:04:37 AM »

So that would also explain the oil leak, right down the slot.


Yes the oil leak, which strangely forgot to mention in my previous post.  :-[ Yes it was the reason for the leak, obviously the oil was coming straight from the tank, and as it was being fed to the side of the pump by a hose it then traveled down the channel and straight out the bottom.

As for the "Chinese knock-offs" I hadn't noticed these, or seen one yet.  I don't think your any worse off with the older type gear head to be honest, new  one's a bit lighter.