Carbon build up in Yanmar 1gm10

[ben_m]

Hi
I took the exhaust elbow off my 1gm10 yesterday and while the elbow itself is fine, the exit on the engine is quite badly gummed up with black stuff. IS there a recommended way of removing this, or should I take the head off? How easy is that to do?

Thanks in advance!

 

[Ubergeekian]

Hi
I took the exhaust elbow off my 1gm10 yesterday and while the elbow itself is fine, the exit on the engine is quite badly gummed up with black stuff. IS there a recommended way of removing this, or should I take the head off? How easy is that to do?

I have just had precisely the same experience.

If you have really good access to the side of the engine it might be worth getting in there with a screwdriver or small chisel and removing the carbon in situ. Otherwise taking the head off is pretty easy - the manuals can be downloaded and it took me about 30 minutes to do, though the exhaust elbow was already off.

Once it's off you can take the opportunity to do a proper head job - decoke, clean up the valves, regrind the seats and so on.

A dire warning, though. What I thought was baked on carbon turned out to be baked on carbon on a heck of a lot of rust. So much rust, in fact, that a little light chipping opened up a hole between the exhaust port and the hole for the inlet pushrod. I needed a new head, and they are £450 here. Luckily I had a friend flying in from the US where the same part costs £300 ...

Good luck. Here's a picture of my lurking horror...

 

[tjbrace]

If you take off the head and decarbonise it, leave some carbon around the perimeter of the piston as it has a sealing effect. I did a full decarb on my previous engine resulting in zero compression. Devil of a job to get it working again.

 

[ben_m]

Wow mine is nothing like that bad - see pic! I should think there's about 5mm buildup, max. Do you reckon it's bad enough to do anything to yet?!

 

[agurney]

Hi
I took the exhaust elbow off my 1gm10 yesterday and while the elbow itself is fine, the exit on the engine is quite badly gummed up with black stuff. IS there a recommended way of removing this, or should I take the head off? How easy is that to do?

Thanks in advance!

I don't know about a recommended way, but I used a handheld mini grinder (a bit like a dremel)) to open the gap a bit. Was too scared to take it back to bare metal though.

 

[steve28]

be warned, if you do it in situ make sure both valves are closed and have a good small suction hose for removing the carbon/rust.

failure to do this will result in the bits going into the cylinder and the piston wont go past top dead center.

the dremel idea works really well with the pink stones.

it doesnt look to bad but cant see much inside.

most people who take heads off end up having valve seats put in on the exhaust, gm engines suffer from a problem if the valve has been lapped down too much the new seat can break into the water way.


steve

 

[Ubergeekian]

I don't know about a recommended way, but I used a handheld mini grinder (a bit like a dremel)) to open the gap a bit. Was too scared to take it back to bare metal though.

I have a pair of decoke brushes which go into an electric drill and work very well if there's room. Mine came from Screwfix, who seem to have dropped them now, but Amazon do a Franklin set for seven quid:

 

[Topcat47]

I'm doing a head job on mine, it's a little over 10 years old. There was very little carbon anywhere and that was quite soft. The seats required a little light lapping using only the fine paste. Of course I have the high level mixer on mine, which is less likely to allow salt water into the engine ( the most usual cause of the head problems mentioned ). Mind you, the cost of the "parts" is well OTT. eg £32.00 for the head gasket (compare to £13 for a complete top end overhaul set for a "real" Mini.

BTW, I used some mahogany offcuts to make scrapers with, if the carbon is soft enough, you don't need wire brushes.

 

[steve28]

The GM yanmars i work on that are coked up on the exhaust ports have either been run for short periods with no load or generaly not run above 3/4 throttle ever. The ones that are worked hard keep the carbon out.


Steve

 

[Ubergeekian]

Mind you, the cost of the "parts" is well OTT. eg £32.00 for the head gasket (compare to £13 for a complete top end overhaul set for a "real" Mini.

Original Yanmar 1GM10 exhaust valves: £22 in the UK, $10 (yes, dollars) in the US. Head gasket $37.25.

 

[25931]

The GM yanmars i work on that are coked up on the exhaust ports have either been run for short periods with no load or generaly not run above 3/4 throttle ever. The ones that are worked hard keep the carbon out.


Steve

Seeing that you work on Yanmars I wonder if you could advise me about compression testing. I'm in the Algarve and can't find a tester to fit - the local diesel people say that they could easily adapt an old injector. Is this a good idea and if so where do I buy an old injector ?

 

[steve28]

second hand ones do come up on ebay but they still go for 40-60 pounds, i would get a machine shop to turn up a blank/dummy injector should only take 10 to 20 mins, from that the injection tester should be coupled easily.

If your concerned about broken rings or glazed bores then the compression test would help, another thing to check is the piston bump stop which is measured by removing the injector on a cylinder, then insert some 2mm solder into the top of the cylinder, rotate the crank by handand crush the solder, if its outside the range ie to thick then the conrod may have bent resulting in poor starting/running.

if its a 1gm10,2gm20,3gm30 then the clearance is 0.68~0.88mm or 0.0268~0.0346 in

if its a 3hm35 then its 0.66~0.86mm or 0.0260~0.0339in

steve

 

[NPMR]

Original Yanmar 1GM10 exhaust valves: £22 in the UK, $10 (yes, dollars) in the US. Head gasket $37.25.

I have a constant complaint that Yanmar parts in the UK (importer = Barrus) are always more pounds than they cost in dollars in US.

When I complained to Barrus they tried to give off some old 'guff' about "special taxes" etc but imported, manuactured metal goods only had 2.5% tax at that time (? still?) so sadly the only difference is that the UK has a much higher mark-up than either mainland Europe or the US. And probably lots more places as well. Part number for part number, the UK is consistently more costly.

If you don't complain, nothing will change. I moaned a lot, and in writing and didn't give up, and in the end, the cost of the mixer elbow (1GM10) I was complaining about, came down, for a short while, anyway.

Yanmar also will not let US dealers export to UK. And Uk dealers seem to be absolutely, resolutely as one about not being competitive. Prices are fixed and no-one offers any sort of discount. Can they still do this in this litigeous and regulated world, I wonder?

 

[Ubergeekian]

Part number for part number, the UK is consistently more costly.

On the bright side, I looked into buying a head in the Netherlands. About £650 there, against £450 here and £300 in the US.

Yanmar also will not let US dealers export to UK. And Uk dealers seem to be absolutely, resolutely as one about not being competitive. Prices are fixed and no-one offers any sort of discount. Can they still do this in this litigeous and regulated world, I wonder?

They won't even let US dealers send to the whole US. Each dealer is licensed for a few states and may not sell outwith these. And, as in the UK, the prices are same to the cent from dealer to dealer.

 

[25931]

second hand ones do come up on ebay but they still go for 40-60 pounds, i would get a machine shop to turn up a blank/dummy injector should only take 10 to 20 mins, from that the injection tester should be coupled easily.

If your concerned about broken rings or glazed bores then the compression test would help, another thing to check is the piston bump stop which is measured by removing the injector on a cylinder, then insert some 2mm solder into the top of the cylinder, rotate the crank by handand crush the solder, if its outside the range ie to thick then the conrod may have bent resulting in poor starting/running.

if its a 1gm10,2gm20,3gm30 then the clearance is 0.68~0.88mm or 0.0268~0.0346 in

if its a 3hm35 then its 0.66~0.86mm or 0.0260~0.0339in

steve

Many thanks, I´ll try that.
Jim

 

[ben_m]

Thanks for your advice, everyone. I think I'm going to go for it and take the head off. I have a little, though not very much, expereince in this type of thing, and have a copy of the manual. Anyone got any tips about it? I plan to remove it, remove the coke, then replace it with new gaskets. Anything in particular I should look out for?

 

[steve28]

Use a dremel with a stone to clean the port back to shiny metal, when you check the valves i think you will find the exhust is pitted on the seat. either take it to a machine shop and check how far the valve is already ground down or measure it yourself. the maintenance is 0.95mm the limit is 1.25mm, if its near the later then i suggest you get a new seat put in with a new valve. seat would be about 9 pounds, fitting about 25-30.

you can get cheaper head gaskets on ebay.

Nothing much more really, PM if you want any more advice.

Steve

Ps dont forget to remove the oil pipe from the back of the head.

 

[Interlude]

BTW, the good book says that at the end of your voyage, you should idle the motor for 5 minutes to allow it to cool, then rev to full revs and back to idle 4 or 5 times to clear the carbon out of the exhaust port and elbow. As far as I can tell, I am the only person in Sydney Harbour to do this, but after I had to put a new head and elbow on my 10 year old Yanmar 1GM10 I have become religious about it. Time will tell......

 

[ben_m]

So I took the head off. There was a small hole in the inside of the exhaust elbow, and the head looked fine. However, as soon as I looked behind the port in the oil chamber, hey presto, a small corroded hole. So, as with many others here, it's a new head and elbow and a reduced bank balance for a few months. Hey ho. Thanks for all the advice, everyone. Just need to get the precombustion chamber out now. Any tips?

While I'm at it, anyone got a new head going cheap?!

 

[Ubergeekian]

Just need to get the precombustion chamber out now. Any tips?

I soaked mine in penetrating oil, heated it as hot as I could in the oven and then tapped it with a hammer. It still broke.

While I'm at it, anyone got a new head going cheap?!

Do you know anyone coming across from America soon? My new head came as hold baggage. They are $505, which is about £300. I bought various other bits as well - thermostat, temperature sender, gaskets and the total bill was £370 as opposed to £600 on the Marine Power website for the same stuff.

My new precombustion chamber is on its way. £127 here, $110 (£67) there. You need to have it delivered in the US, then sent on here.