Can't get bike to run right

[tony27]

Do you think this might be the cause?

Have a spare sidepiper barrel drilled to take the radial head but not got a 1st oversize piston for a 380 thats usable

[090]

Ouch! What the hell causes that?

[tony27]

No idea although it's been welded up before through the transfer port & at the front sometime in the distant past.
Bike has been in the family for at least 20 years so must have been prior to then
Starting to think seriously about removing the liner to have it fixed properly & fitting the liner to the sidepiper barrel that needs a piston

[VMX60]

Tony
Had this same problem with two cz 380 barrel no idea at the time my this happen having run cz for over 8 year plus in VMX
The first one i had welded and machined overall cost turned out more then a buying a barrel ex usa 2nd time around that what i did EBAY  saved the day

The reason from all the experts  Ron Gill etc
CZ never do that
You must have left a piece of the old base gasket on the cases
Must use CZ gen large barrel stud nuts with washers
Overtighted the barrel nuts when the motor was hot

And the list goes on anybody on this board know the real WHY
Please let us all in on the secret

Cheers

[GMC]

I have come across a couple of barrels like this over the years.
They were all down pipes.
One theory was that if the down pipe hits the ground at just the right angle it can cause upwards pressure causing the barrel to lift.
Porous castings might help to create the problem.

Removing the liner to weld is preferable.
I welded a CZ 360 twin port barrel with the liner in once (it was a Sat. arvo before Ravenswood)
Welding up against the steel liner is difficult but I managed to seal everything back up. I could have done a better / easier job with the liner out.

[tony27]

So does swapping the liner into the spare barrel which I don't have a piston for sound the best option in the time being?
Any idea what size the nuts should be across flats,presently they're 14mmAF with spring washers underneath





Few more photos of the weld now everything is clean

[VMX60]

Tony
The gen CZ barrel stud nuts are 17mm spanner size have to use a open end about half a turn at a time as there is no room to use a ring spanner

GMC theory of the pipe hitting the ground  sounds  as good as any
Another is running to much piston skirt clearance
All the barrels seam to break on the same side as yours which has and the lower ex stud  right there

Changing the sleeve will also mean checking the bore to piston skirt clearance if using the s/h piston and sleeve you have ??

Cheers

[tony27]

Put barrel in oven at work just before lunch, left in from cold about an hour at 200C standing on the sleeve.
By the time I went to remove it from the oven it was sitting on the flange, tipped it upside down & the sleeve slipped out under its own weight
Dropped it off to the welder after work & he thinks it should be weldable, pick it up tomorrow arvo with any luck

[tony27]

Picked barrel up after work, nice job for $130.
Unfortunately after tidying up weld in bore & transfer port I checked flange with a DTI & it will need building up some more as the welded portion has warped upwards by .2mm even though it was welded held down to a plate-not unexpected though.
Will see if it can get done tomorrow.




Tried option B but sidepiper sleeves are smaller diameter, I'm guessing around 2mm to go with the 80mm instead of 82mm bore.
Removing & then replacing the sleeve was a lot easier than expected, 200C for around an hour lets it drop out.
Replacing the sleeve was just as easy, hadn't put sleeve in freezer as wasn't expecting to be putting it back in but it dropped back in & I had several minutes to align the ports if needed

This weekend obviously wasn't meant to be 

[GMC]

A small amount of warpage of the broken piece isn't that unusual.
Even though it is clamped down, when things cool they can change.
Still .2 mm doesn’t sound much. You could possibly “surface grind” it on a thick sheet of glass with some valve grinding paste, moving it around in circular motions.
Building it up will be good but it is hard to take it back to the right level if you don’t have access to a Milling machine.

This weekend obviously wasn't meant to be 

Its not too late until the early hours of Sunday morning

[tony27]

I'm a toolmaker with a very understanding boss so access to machines is no problem, another option could be to machine an amount off the face & use countersunk screws to attach a spacer plate to bring thing back to correct height
Finding a replacement cylinder will have to go on the list for the future

[GMC]

I would have thought 0.2mm would be neither here nor there.
It would make minimal difference to the port timing and only a slight increase in compression.

A spacer plate sounds make shift and would be a recipe for future problems (air leaks) and that is no slur against your talents for fitting it correctly.

If the you wish to maintain the correct deck height then best to have it built up.

[jimg1au]

spoke to my mate in navarda and he said there are a few sleeves arround to buy will set you back over 200.00 usd + air mail about 49.00 usd
jim

[tony27]

Jim, could you ask your mate to keep an eye out for a radial head cylinder. Sleeve isn't the thing I'm concerned about

I took the cylinder to show the engine rebuilders down the road from work & see what they advised, their suggestion was to get the base flat & make a thicker gasket to correct the difference if it needed
After work I screwed 3 ground plates to the top of the barrel in place of head studs & then ground the base flat, ended up removing exactly .3mm. I planned on making a .8mm thick copper head gasket but after seeing GMC's post I decided to see whether there was enough clearance between piston & head, turns out there is
Bike is back togethor & it starts but due to it being 9pm & the neighbours have a young child I'll have to leave it til tomorrow to get it hot

[Bamford#69]

Hi,
Are you using a 360 Sidepipe barrel and head , pre 70 360's have 5 studs , 5 stud radial fin heads are available,but rare and expensive , if you have a 6 stud barrel or  head  just check its not a later set off a pre 75 380/400
cheers