Honda UMS425 Bent Shaft Questions & Answers

The needle on the rotary valve of the carburetor needs to be adjusted, most likely out (anticlockwise) as it seems like it may be running lean on idle. This often happens when the internal carby parts harden from E10 fuel, or it is an older machine. Later model machines require a specialised tool to do the adjustment, most mower shops toss the carby and fit a new one as adjusting correctly is a specialised skill.

Thanks Craig, I was thinking of replacing the carby. Quite cheap on EBay but gave it one last go as I was getting annoyed with the grassy edges. I readjusted the throttle cable ignoring the 1~3mm idle free-play and low and behold it started idling. I added about 10% Metho to the tank to deal with the methanol residue and so far so good and will continue doing this for a while. If this occurs again a new carby is on the cards. Cheers

Your best bet would be to ask Honda themselves.
I have used mine at many different angels from flat right up to 90 degree and it was fine.

Hi Greg,
Yeah, I have had no problems using at any angle including upside down and 90deg doing edge trimming. If the fuel level is low in the tank, the fuel pick-up(even though it is on a flexible hose) might not sometimes be immersed in fuel and that would be the only time I could see you having a problem. The carbys in these small engines don't rely on a float in a bowl arrangement and hence will work at any angle.
These engines only hold a small amount of engine oil(less than 100ml) that is getting splashed around everywhere and don't have a sump that can dump a whole lot of oil on the underside of the piston if inverted.

I purchased a new Speed Feed head from my Honda supplier (Parsons in NSW), 72560-UMS-OW4, which works really well (didn't have a chance to test it until now). You can feed the new line in without taking it apart and it bump feeds the line really reliably. Only around $40, pretty much the same as the non Honda heads.

DO NOT USE FUEL WITH ETHNOL, I always use 95 octane with out ethanol... Ethanol in fuel attracts moisture [water] and causes corrosion in carburettor and other components.........

Regards
Stewart

Thanks Stewart!

Any 91 Ron or higher octane fuel will be fine.

According to Honda, http://powerequipment.honda.com.au/Domestic_Brushcutters/UMS425_Bent_Shaft, 0.08 litres or 80 mills. I change mine every 12 months. After use, when oil is hot, drain oil and refill. I refill to the bottom of the cap threads, run, then recheck the level.

Was the fuel fresh? How many times did you pump the primer? Might be a clogged Carby. Did you take the spark plug out and put a small amount of fuel in? If this starts it, could be a fuel blockage, best to get it looked at. Just a hint, the gear box ($280) needs to be greased at lease once per year. The gear box is located just above the cutting head, with access via a Phillips head screw. A mower dealer should have a tube of grease.

Firstly let me suggest that you take it to a Honda dealer and get it checked. These are a good machine and not cheap so best get it done properly so you are not wasting money by junking it.
Secondly, the most common thing if they have been sitting around is either fuel/fuel line issues OR the spark suppressor unit has been blocked by ants or wasps building a nest. Either situation won't be expensive to rectify and again I suggest you take it to your Honda dealer.

Fuel goes off after about 3 months--it will need to be replaced and the system flushed.
It's a good idea to use fuel stabilser in fuel used for garden gadgets to avoid this problem.

I've heard 2.4mm. I "ditched" the bump feed rubbish at sale hand had them install the alloy wheel with single feed. I drilled the holes to 3mm, and this works great. Each to their own though, I find the alloy wheel, while you do waste more, to be less frustrating when the "bump feed does not work, which is often. However, there are many different combinations now, that could be ideal.

Thanks GK. I should have read through the existing Q&A before posting as it had been asked a few times before. The range of 2.4 to 2.7 seems most common, so I picked up a roll of commercial grade (twisted) 2.7mm from Bunnings yesterday. Paid about $11 for the 10m roll. Cheers.

Hi nick no its not possible to change the rotation of the cutting head

Yes flip it upside down

Hi Albo,
Did a quick internet search and located the user manual at:. http://www.manualguru.com/honda/ums425u/owners-manual

The trimmer Line, as with most trimmers I've tried, is a pain to change. The reason I originally bought a Stihl was because it had a beautifully simple wind-on Line feature. Unfortunayely, I had extreme difficulty starting it, so traded it for the Honda.

I have seen trimmer head replacements that hold 3 or 4 loops of trimmer Line and bought one for my old Homelife trimmer. I'm not sure if there is one available for the Honda - if anyone knows of one, please let me know. On the Homelife it made Line replacement a simple and short process.

Regards

By the way, I found the following video on YouTube which shows how to thread New Line on your trimmer head.
https://www.youtube.com/watch?v=XCtEn_fRL6U

Hope it helps.

Thanks IanKen. The manual doesn't give you any info on changing the line but the youtube video does. The video is very good. Thanks

If memory serves me correctly you should be using a 2mm diameter string. My dealer told me that the star shaped nylon string is better cutting and stronger than the round variety. The only problem with nearly all strings I've tried is that they tend to jam on occasion if you are not really careful about winding it on. There are after market cutting heads that use straight cord. They are easier to thread and tend to last longer between changes. Check that they won't upset the balance of you trimmer and, thus shorten it's life expectancy.

Sorry, IanKen. I think my question was misunderstood. I have purchased a new bump head which has a larger internal threaded diameter than the threaded bolt on the end of the bent shaft which affixes to the bump head. I wanted to know how to fix this anomaly - is there a coupling that can be placed over the threaded bolt to expand its diameter? BTW I currently have square shaped nylon thread which works brilliantly - last longer and cuts infinitely better.

Sorry, I don't know about this one. My guess is that you probably need to have a mower mechanic look at this. My Honda is a curved model which, I think, has a cable drive. I assume yours is a straight shaft which has a gear set at it's base. It may be cheaper to buy a new gear set.check with Honda.

My machine has a bump feed head. First remove outer case by pushing in opposite side tabs. Cut about 2 metres of cord give or take. You'll find two small holes on inner cord holder. Feed cord through one hole to inside and then out other hole from inner holder to out. Even up cord coming from either hole. Wind one cord clockwise round one side of inner holder and other cord clockwise round other side of cord holder. Leave about 100mm hanging out and don't let go. There are slots to hook cord onto while placing inner holder back into casing. Once in pull cords into holes where cord normally flows. Still try not to let go. Replace outer case making sure to align properly and secure. Run motor and tap to extend if needed. Only trick is both ends wound around same direction.

https://youtu.be/z8CoQZvq3ss

Any authorised Honda dealer should be able to get that part!

I use 2.4 line

I use 2.7. It seems to do the job for me

do you use it at full revs maybe try it and see how it goes then