One for the small engine experts (GX35 burning oil)

[Crossy]

Our 10 year old Patco-Honda brush-cutter has become increasingly difficult to start and now is definitely burning oil (exhaust smell), it also tends to peter out and stop. It's had a pretty good life really (Madam's family bought a cheap 2-stroke, it lasted less than a week).

 

So, I bought a new one, brilliant!

 

The engine on both is a Made in Thailand, Honda GX35. 

 

So now, is it worth re-building the old one? I can get a carb (with a "free" rebuild kit) for less than $20 and a piston with rings and gudgeon pin for less than $10.

 

I've not had the engine apart yet so I don't know what the bore is like, but assuming it's OK it's an engine re-build for $30 plus my time.

 

Question is, is it really worth it? Or should I just buy a whole engine?

 

[billd766]

I had a similar problem with mine and took it down to Somchai Fixit in the village. 

 

He took it apart and found that it was beyond his skill level to repair. He showed it to me and told me that he could send it away and get it rebuilt. 

 

It took a couple of weeks and a couple of thousand baht and came back as good as new.

 

It is definitely worth it.

[cornishcarlos]

Always a dilemma these days... I would say do it, just for your own satisfaction, if you have some free time... 

I just got home for a 2 week holiday and straight into a washing machine draining issue !! I bought a new one for 6000 baht, as this old one is about 6yrs old.. It just wasn't worth using up my time with this problem but I will sort it out at a later date. I know what the issue is after spending an hour on it... 

 

$30 is worth spending to have a reliable back up machine ?

[thoongfoned]

we tend to buy new every 5 or so years, this year bought the honda gx35 also, just over 6,000 baht at dohome, i think they have got cheaper this year? before 8 or 9,000 baht? have many old hondas/makitas... still kept them running/fixing but at 6 ish new i will just buy new in the future.

[impulse]

 

It's a math problem with a lot of unknowns:  

 

How long will it take?

How much are the parts (and tools) really going to cost to do it right?

What $0.50 part is going to delay the job when you can't find it locally?

How much is your time worth- including the time scrounging parts and tools?

What are the odds of screwing it up?

How much would a new Honda cost?
How long would a new one last?

Would a local brand like Polo (at half the price) be more cost effective than a Honda?

How much goodwill in the community can you get from giving the old one away to a neighbor with time on his hands?

 

If you enjoy working on engines, have plenty of time, and take pride in fixing your own stuff, go for it.

But even as a former grease monkey and semi-retired mechanical engineer, I'd go with a new Polo and cross my fingers.

 

[johng]

. I know what the issue is after spending an hour on it

Dodgy solenoid ?

[Crossy]

The carb definitely has issues, the check-valve on the primer lets air back and I suspect the diaphragm is on it's way out, for the cost of a new carb it's not worth faffing about re-building it. I'll probably end up doing it anyway mind, for a spare.

 

New piston with rings is on the list, I can re-grind the valves if they need it. As noted the cylinder is the most expensive bit, if it's badly worn or scored then time for a new engine, so task A is to pull the beast apart and have a look.

 

It's been a looong time since I re-built an engine, the last one was the Ford 2L cross-flow from my Transit (with a Capri cam and twin-choke Weber, went like a bomb, swallowed 4* like there was no tomorrow), probably back in 1990. The smallest I've done was a 250cc Matchless single (I wish I still had it, they fetch $$$ now), so 35cc is going to be fun, I have my head magnifier.

 

Once it's sorted I'll likely donate it to family ?

 

[Crossy]

3 hours ago, cornishcarlos said:

$30 is worth spending to have a reliable back up machine ?

And of course, I will be embarrassing myself by posting the gory details on Thaivisa.

 

[canuckamuck]

Go for it, I might do the same. But I am liking the backpack version of the gx35 as well. I might fix the old one and still get the new version.

[billd766]

I have attached a list of parts in XL for the past 3 years.

 

A genuine Honda carb was 900 baht last year but you can get a copy for 600 baht.

 

Here is a link from the UK on all the parts for the Honda.

 

It gives the drawings and also the genuine part numbers.

 

http://www.diyspareparts.com/parts/honda/diagrams/umk435e-ueet/air-cleaner-7/

 

 

UMK 435 replacement parts cost.xlsx

Edited August 19, 2018 by billd766

[GregTN]

Remember that a cylinder never wears in a perfect circle but egg shaped due to gravity and piston thrust. The old rings wore in the same manor so they fit but now loosely. A new set of rings will be perfectly round and not fit the egg shaped bore.


Sent from my iPad using Thaivisa Connect

[Isan Farang]

41 minutes ago, Crossy said:

And of course, I will be embarrassing myself by posting the gory details on Thaivisa.

 

 I just finished a service on my strimmer with the GX 35 unit, still had the same issue with the engine cutting out after 15 min of use, I bit the bullet and let my Mr Fixit have a look, he told me it was the coil and after changed its been perfect.

 

 

Carburettor check sheet GX25-GX35.pdf

doc.pdf

[Crossy]

13 minutes ago, Isan Farang said:

still had the same issue with the engine cutting out after 15 min of use,

Ours sort of fades out once it gets really warm, I will certainly bear the coil in mind (it's actually a magneto, but the semantics matter not for our purposes).

 

One great thing about these ubiquitous little engines is that there are millions of them (and copies) out there so spares are readily available and low cost.

 

We have the advantage of being within easy striking distance of the farm shops at the back end of Rangsit market, never been let down by one or other of the "it's in here somewhere" shops ?

 

[Isan Farang]

3 hours ago, Crossy said:

The carb definitely has issues, the check-valve on the primer lets air back and I suspect the diaphragm is on it's way out, for the cost of a new carb it's not worth faffing about re-building it. I'll probably end up doing it anyway mind, for a spare.

 

New piston with rings is on the list, I can re-grind the valves if they need it. As noted the cylinder is the most expensive bit, if it's badly worn or scored then time for a new engine, so task A is to pull the beast apart and have a look.

 

It's been a looong time since I re-built an engine, the last one was the Ford 2L cross-flow from my Transit (with a Capri cam and twin-choke Weber, went like a bomb, swallowed 4* like there was no tomorrow), probably back in 1990. The smallest I've done was a 250cc Matchless single (I wish I still had it, they fetch $$$ now), so 35cc is going to be fun, I have my head magnifier.

 

Once it's sorted I'll likely donate it to family ?

 

If you into ford engines and a company with a machine shop second to none then check these guys out, I used them more than 40 years ago and they are still alive. http://www.burtonpower.com/

[Isan Farang]

48 minutes ago, GregTN said:

Remember that a cylinder never wears in a perfect circle but egg shaped due to gravity and piston thrust. The old rings wore in the same manor so they fit but now loosely. A new set of rings will be perfectly round and not fit the egg shaped bore.


Sent from my iPad using Thaivisa Connect

To state that a cylinder bore is egg shaped would be an assumption, to measure with a calibrated ID Micrometer would provide the facts

[Crossy]

On 8/19/2018 at 7:06 PM, Isan Farang said:

To state that a cylinder bore is egg shaped would be an assumption, to measure with a calibrated ID Micrometer would provide the facts

Indeed, but we're not talking F1 here, I'll do a straightedge and feeler gauge wear check and if it's not too bad it's getting new rings.

 

[Isan Farang]

3 minutes ago, Crossy said:

Indeed, but we're not talking F1here, I'll do a straightedge and feeler gauge wear check and if it's not too bad it's getting new rings.

 

For a run of the mill small engine like this I would just take some very fine emery paper and deglaze the bore and fit new rings.

[Crossy]

2 minutes ago, Isan Farang said:

For a run of the mill small engine like this I would just take some very fine emery paper and deglaze the bore and fit new rings.

I used to use a length of emery cloth taped to a twist drill in my Black and Decker, a sort of one-legged flap wheel. Deglazed the bore like a dream, time to re-live my youth methinks.

[NonthaburiBear]

Burning oil mean theres something wrong with the Oil Seal. nothing wrong with your piston or cylinder ( might be in many cases your not needed to change, but if you think its false economy , change it as well ) .The burning smell coming from the oil consume by the carb and going to your cylinder. One thing you need to check is the oil capacity, if decrease then you have  leakage on the oil seal.its not worthed to get a new one as if its only need to change the seal

Edited August 19, 2018 by NonthaburiBear

[NonthaburiBear]

2 minutes ago, Arjen said:

What oil seal?

The oils seals on a four-stroke engine are the piston springs and the sealings on the valves?

Arjen.

ahh sorry..i tot its GS150 engine.mai pen rai

 

[Isan Farang]

7 minutes ago, Arjen said:

What oil seal?

The oils seals on a four-stroke engine are the piston springs and the sealings on the valves?

Arjen.

 

3 minutes ago, NonthaburiBear said:

ahh sorry..i tot its GS150 engine.mai pen rai

 

Can you post me some of that herbs you are puffing.

Edited August 19, 2018 by Isan Farang

[NonthaburiBear]

4 minutes ago, Isan Farang said:

 

Can you post me some of that herbs you are puffing.

Mushroom..come to my place its free

[Isan Farang]

8 minutes ago, NonthaburiBear said:

Mushroom..come to my place its free

 

8 minutes ago, NonthaburiBear said:

Mushroom..come to my place its free

Only if you play Pink Floyd and you get your shit together on the Honda GX 35 Engine

[Isan Farang]

33 minutes ago, Arjen said:

What oil seal?

The oils seals on a four-stroke engine are the piston springs and the sealings on the valves?

Arjen.

Tell us more about the Piston Springs

[Isan Farang]

2 minutes ago, Arjen said:

Not mutch to tell. It are springs around the piston. The upper two or three are to close the gap between cilinder and piston for the gasses created with the combustion. The lower two or one are to remove the oil from from the cilinder. 

 

Probably I used the wrong words? I hope this clarifies it a bit.

 

Arjen.

No problem Piston Rings was the word you were after.

[NonthaburiBear]

49 minutes ago, Isan Farang said:

 

Only if you play Pink Floyd and you get your shit together on the Honda GX 35 Engine

nah..didn't into PF, mostly Rolling Stone ..cheers

[Crossy]

No worries @Arjen we know what you meant.

 

The thing that always worried me about putting rings on is the amount you have the stretch an apparently inflexible lump of steel. I never broke one much to my surprise, but these GX35 ones are only 39mm in diameter. Scary.

 

[NonthaburiBear]

2 hours ago, Crossy said:

No worries @Arjen we know what you meant.

 

The thing that always worried me about putting rings on is the amount you have the stretch an apparently inflexible lump of steel. I never broke one much to my surprise, but these GX35 ones are only 39mm in diameter. Scary.

 

try to put the piston in refrigerator, steel tend to shrunk when cold...so you can bent the ring not too wide

[kickstart]

23 hours ago, Isan Farang said:

Tell us more about the Piston Springs

I think he means valve springs if you do remove the valves use new valve collets when putting the valves back in, and check for wear in the valve guides, should not be a problem .these little engines are pushrods, so . check the valve clearance, can be critical 

Isaan Farang, the lower piston ring we call it the scraper ring, scrapes the oil off the cylinder walls.

Fitting piston rings ,is a bit of a sharp intake of breath ,amazing how they stretch, and do not do what I did once putting the cylinder  back on one of the rings would not go in to the cylinder ,found the ring had mover a bit  and was not located on the peg on the piston ,once I found that out it went on no problem , 

Once did a BMW motorbike had to use a ring compression tool they where tight.

[NonthaburiBear]

5 minutes ago, kickstart said:

I think he means valve springs if you do remove the valves use new valve collets when putting the valves back in, and check for wear in the valve guides, should not be a problem .these little engines are pushrods, so . check the valve clearance, can be critical 

Isaan Farang, the lower piston ring we call it the scraper ring, scrapes the oil off the cylinder walls.

Fitting piston rings ,is a bit of a sharp intake of breath ,amazing how they stretch, and do not do what I did once putting the cylinder  back on one of the rings would not go in to the cylinder ,found the ring had mover a bit  and was not located on the peg on the piston ,once I found that out it went on no problem , 

Once did a BMW motorbike had to use a ring compression tool they where tight.

bit of oil on the piston will make the ring flush into the gap and turn the ring until found the pegs