Lister Engine Forum

How to / DIY => Engines => Topic started by: veggie on May 31, 2019, 10:56:09 PM

Title: Head Bolt Torque - Changfa 175
Post by: veggie on May 31, 2019, 10:56:09 PM
Hi All,

I am replacing the head gasket on my Changfa 175 and I do not have any specs on the torque rating for the Nuts. The Head Nuts take a 19MM socket and the studs are 12 mm fine thread.
Any ideas or rule-of-thumb for a torque wrench setting on these nuts?


   [ click picture to enlarge ]
Title: Re: Head Bolt Torque - Changfa 175
Post by: cobbadog on June 01, 2019, 06:49:32 AM
At least you have a thread size and that is great. Use Google and get a 'torque settings for a 12mm bolt. Sometimes it will want to know fine or coarse thread so if it is a fine thread it will be 1.00mm pitch and not 1.25mm.
Title: Re: Head Bolt Torque - Changfa 175
Post by: glort on June 01, 2019, 08:43:03 AM

I took the head off my 165 several times and just torqued it down tight which being me, is pretty tight apparently. Never had any problem.

I bet there are thousands a year serviced in the field in the Asian country's and I'll also bet the amount that are done up with a torque wrench could be counted on one hand!  :-[

 From the numerous Vids I have seen, most of them are real lucky to have an air filter!   :o

Come to think of it, I don't ever remember even thinking of the torque settings for the head of any small engine I have rebuilt.  More than one had gaskets including head gaskets cut out from a cornflakes box or other single ply cardboard.
I remember doing one as an experiment where I only cut a small  hole in the bore area.  I was right, fuel got pushed through there, cardboard burnt away and made its own fit.
Title: Re: Head Bolt Torque - Changfa 175
Post by: old seagull man on June 01, 2019, 12:59:08 PM
Might help.

my zs 195 manual says head bolts to 25 kgf.m (kilogram force meter)
If my math is correct that's something like  180 foot pounds.
Title: Re: Head Bolt Torque - Changfa 175
Post by: veggie on June 01, 2019, 07:22:18 PM
Thanks guys.
I used that online torque guide you suggested and it recommended approx 100 ft. Lbs.
So that's what I did.
Squished the gasket good and tight.

Later dudes !
Title: Re: Head Bolt Torque - Changfa 175
Post by: cobbadog on June 02, 2019, 05:07:47 AM
I too have used the corn flake packet for my model 1 Victa over the last 50 years plus. I took the ehad off a B&S 4hp to do a valve grind and re sealed it using a head gasket spray I had left over from the grey fergy rebuild. I also just used my sockets and pulled it up tight with no issues so far.
Title: Re: Head Bolt Torque - Changfa 175
Post by: glort on June 03, 2019, 12:30:01 AM

The Victas were a terribly under rated engine.
I used to hot those thing up and do stupid things with them as far as RPM and output and never once did I break one. 
Far tougher than nails!

Briggs OTOH..... They were fragile even at stock HP and the price of parts was just a bad joke. I know people love them but back when I was playing with them, they would make a listeriod look like precision engineering. They had like 8 head Bolts on a side valve design which was low compression and the minute you bumped it you ran into problems with spitting gaskets or stripping the bolts out the aluminium blocks.

Not just the Punjabs that have put together poorly built engines. I hear they are better now, Couldn't have got much worse and I think they were going out the back Door with Honda overtaking their market.  Irony here is Briggs now own the Victa brand and fit Honda motors to their Products.
I cant remember too many cases of one manufacturer using a competitor product  they made a direct alternative to but goes to show the esteem each one has in the marketplace.

I'll bet now the Biggest threat all the small engine manufacturers face is not from one another but the very good and cheap engines the Chinese are pumping out by the million.
Title: Re: Head Bolt Torque - Changfa 175
Post by: cobbadog on June 03, 2019, 06:53:41 AM
I too went down the road of improving performance with a high comp head ram air injected by use of a megaphone inlet tube and megaphone exhaust, enlarged ports and inlet with a motor bike carby to fuel it along. Still never broke it.
With B&S buying Victa only to shut down 2 stroke production as not many buyers wanted a 4 stroke never mind a B&S piece of s**t. But GMH went and use Nissan motors in the Holden Commodore to get it to move along but had cooling issues with it, until they realised the problem and then resolved it.
Title: Re: Head Bolt Torque - Changfa 175
Post by: glort on June 03, 2019, 09:46:28 AM

The Power Torque engines were Rubbish but the 160cc before it with the separate crank case and barrel were great.
Why they went from a Full crank to a half with stamped con rod can only be described as a bad mistake no matter what the cost savings.  Those things weren't a pinch on the old motors.

I still have one of the mowers up the back with the original 160cc they stopped making in '84. Now and then I drag it out and fire it up and just listen to the thing.  Brings back childhood memories of waking up on a weekend to the sound of people mowing their lawns and THAT was what a mower sounded like and always did till much later.

I always say, people who don't like 2-strokes and think they are hard to start or don't run well or whatever just don't know how to tune them and what makes them tick.  When set up and tuned correctly, they are a Marvellous sound to behold in any type and application.
Title: Re: Head Bolt Torque - Changfa 175
Post by: cobbadog on June 04, 2019, 06:44:42 AM
I have many Victa mowers of various models and one was drageed from a drain that floods each time it rains. This mower went under water all the time. Siezed I took it home and soaked the top n bottom ends in auto transmission fuid and accetone. Next day with a small amount of help from a breaker bar it freed up. I chased the mud crabs out of the carby n fuel tank and rebuilt the carby and it started and still does. It is a full crank engine and the carby is one with the grey knob on the outside that actually does alter the hp slightly. IT is one of the 'go to' mowers for slashing down long grass but the favourite is either the Model 1 or 2 which ever is closest. No grass catcher to get blocked up. We have an early 1990 Silver Streak bought from new and now is a Rally mower mower painted in 2pak and bright pink as it belongs to my wife. Any mower that is late model I convert them to being mulchers and the same for the ride on too.