OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Victa v40 Chonda Smoking badly

Hi Guys,
I recently acquired a Victa V40 Chonda from the local recycle centre. I have come across quite a few of these and the vast majority after a good clean up function well.
This mower was an exception because it was missing a starter and the carby was badly damaged simply because the previous owner didn�t know how to remove the carby studs from the block. I ordered a new copy carby for the GXV120 and the mower was back up and running after the general once over.
Work to date,
- Cleaned spark plug � good condition with nice blue spark
- New gxv120 chonda carb as the previous carby was beyond repair
- Valves adjusted according to spec. .15mm inlet and .20mm exhaust
- Re-adjusted the linkages to get nice one pull starts
- Changed oil as it was pretty black and sludgy.
The mower started up quite easily however it was blowing smoke which make me think oil was in a combustion chamber. Further inspection revealed oil in the breather tube which made me take off the flywheel and check the pcv valve. I cleaned the area thoroughly and found the disk in good condition with no noticeable faults. Their did not appear to be any blockages.
I started the mower back up after cleaning the pcv system and still the same problem. I.e smoking badly. I doubled checked the choke operation and it opens and closes perfectly so the mower is not stuck on choke. This repair did however remove the vast majority of oil from the breather tube area.
I tested compression and its 115 psi after 4-5 pulls of the rope which I though was pretty reasonable.
After doing some reading I though the head gasket might be shot between the cylinder and the valve chest. Inspection revealed this wasn�t in fact the case well judging by the condition of the head gasket.
The valves were really chocked up with carbon so I completely dismantled the head and lapped the valves � all appeared to be in a good condition.
The cylinder bore was in excellent condition with no damaged noticeable.
This is the strange thing � see my photo of the head gasket and the fact it doesn�t line up on the head via one of the oil cooling galleries. I�d like to know if this could be the problem because I am a little stumped at the moment.
The gasket only has very minor damage on one of the corners however I am thinking it might be best to get a replacement unless you guys think otherwise.
As usual any suggestions on this job would be appreciated.

Jaffa

Hi Pete, i dont like the way the head gasket lines up but i don't think that would be causing your problem. How long did you run the machine for? Could the muffler be excessively wet with oil. I once had a briggs that took about 15 mins to carbonise all the oil from the muffler. Reassemble and start it without the muffle fitted to see if it still smokes up as before.

Hi Jaffa,
Just wondering if you're perhaps using the old fuel (if there was any) in the machine when you picked it up? If so, I wonder if they were using 2-stroke fuel mix in a 4-stroke... would explain all the combustion chamber carbon, oil contamination and smoke?

Just a thought,

Thanks Theo, I didn't like the way the gasket lined up either. I have never actually seen one not line up before on an Over Head valve engine. I also noticed the bolts were not torqued correctly when taking off the head. I re-torqued them up correctly according to the GXV120 Head Bolt Torque Specifications.

Good suggestion about the muffler. I only ran it for 10 or so minutes so I swapped the muffler over to see if that makes a difference tonight after re-assembling the engine. I have to wait until tomorrow to give it a good run.

Re the fuel - the first job I get with all mowers is to drain the fuel, clean the tanks and replenish with fresh fuel.

I was thinking the fact the head may not have been torqued correctly could be an issue.

Open to suggestions.

Jaffa

Well I put it all back together and still the same problem despite the head now being torqued correctly.

The mower starts easily on choke at full speed it only blows a little smoke but still way to much for my liking and when you back it off to idle its smokes like crazy.

I swapped the exhausts and the same problem was still evident.

The PCV breather is fairly clear and doesn't appear to be at fault like before it was cleaned.

I am still leaning towards oil getting into the combustion chamber somehow but I am a little unsure.

Also I know the chonda copy carb I got is correct as I have used them on copy GXV120 engines before and they have not caused an issues.

If the rings were damaged I wouldn't get decent compression.

Any chance a new head gasket could fix the issue?

Still thinking and would appreciate any thoughts!

Don't know the engine design so only speculations- maybe they'll give you an idea or two-

Firstly I assume it's blue oil smoke.

- any likelihood of oil leakage past the valves- seals?
- if there's an oil scraper ring, could it be upside-down?

Good luck!

Could be a broken oil ring. it wont necessarily damage the bore and would let enough oil in to blow smoke.
My 20 cents worth.

Ok now I am thinking this might be a prime opportunity for a leak down test otherwise I will be cracking the case, undoing the rod bolts and sliding out the piston so inspect the oil ring. The leak down would verify valve leakage, head gasket issues or potential ring issues the compression test did not reveal.

I've always thought of buying my own leak down tester but never actually bought one. I'd appreciate some more experienced thoughts.

If I crack the case it is likely I am most likely going to damage crank seals and the case gasket. A set is around $30. If this was a Honda, Briggs Industrial Engine, Briggs Intek or a Kohler engine etc I wouldn't hesitate spending the extra money but on a Chonda I need to draw the line at a certain point.

Anyhow thoughts would be welcome.

I am working on one of these now.
Compression 60 psi.

I have recently bought a leak down tester and have used it a few times. I am in the process of learning to trust my piece of test equipment.

An example: On the engine above, what I call a lot of air was coming out of the oil breather.
So I it needs rings.

I made an adapter and I connect it up to a tyre pressure pump, it gives me enough air to do the testing.

I have sealed quite a few now with RTV silicone and they dont leak oil and the end play on the crank is ok as the silicone has some thickness to it, not sure what others do. I have cut them out before using a ball pien hammer and a manilla folder.

If you suspect valves as Pitrack 1 has said, prior to opening it up, try another head if you have one.
Always tough when you are trying to keep the job economical, but trying to maintain good standards and not have to scrap the engine.

Only 2 places it can pass oil, past the oil ring, been caught recently with 2 motorbikes doing this with rebore, new pistons and rings or through the guides. My guess is oil ring

Guys, I appreciate the suggestions. The oil ring is looking more and more likely. I assume their is no way to test for this fault without cracking the case, un-doing the rod bolts and sliding the piston out.

I also wanted to confirm that is ok that I seal up the crankcase with rtv silicon when I crack the case, that's of course of the gasket gets damaged. Being a fairly new mower I hope the crank seals will be ok.


Mark, I have been looking at a few different versions of leak down tools on ebay and through normal retail shops. Can I ask what you bought and the rough pricing?

I'd appreciate anyone else's thoughts on the value of a leak-down tester for general hobby use only.

Silastic is perfect if you dont want to buy a new gasket. Just let it cure for 24hrs before you start the engine after re-assembly.

Not being familiar with the motor, why do you need to split the cases just to replace the rings?

G'day Jaffa,
I got this one.
I was going to buy all the parts and make one.
I have been getting by without out one, but it is now there when I need it.
http://www.ebay.com.au/itm/190734276084?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks Mark that was the same one I was looking at. Will do some more reading on the concept and probably purchase one.

Ok, I have done a little more research on splitting the case and it appears worthwhile. I have found a full set of rings (including the oil ring) for $12 delivered that's if I find the oil ring is damaged.

This is a GXV120 motor and unless I am completely mistaken I'll need to crack the case, undo the rod bolts and slide the piston out. I have watched several similar video's on u tube but I am after a few pointers before I commence this task.

I'd like to specifically know what to watch out for and some pointers to make sure I execute the project correctly.

I know to carefully:
Look for the timing marks and use a marker to ensure they line up if timing marks are not present
Put a mark on the piston to ensure it is re-inserted into the bore the correct way
Torque the rod bolts correctly

What I need to confirm is?

Do I need to hone the bore similar to inserted new rings on a 2 stroke given this one has minimal wear?
The recommended torque specs for the rod bolts and the case when I re-seal it with RTV silicon. Well at least a recommendation based on experience would be greatly appreciated.

Any other pointers would be appreciated.

Thank you

Hi Peter, a light hone will definitely be needed, to knock the shiny glaze off the bore. As for torque settings i'll look them up in the honda manual if i can find it and report back here.

To put an end to this thread. I dismantled the engine and found a damaged oil ring as well as a damaged bore low down that I couldn't originally see with the head off so the engine turned into parts.

It was worth more as parts to fix other mowers. If it was a Briggs Industrial/ Commercial Unit or a Honda I would have re ringed it.

Thanks all for the assistance.

Peter