GPR Camp: Replica Racers

Isn't there suppose to be some kind of o-ring? I mean between water hose adapter and water outlet? There was none supplied...

Sure looks like there should be something.

Is there a groove for one on the black piece?

How is it held in place? I don't see any interior threads.

There is fine thread inside:

Jaxx wrote: ↑

Sat Jun 20, 2020 10:30 pm

There is fine thread inside:

Ah - thanks.

Is the black piece aluminum or plastic?

It may be designed to seal at the bottom of the opening. I don't see any place for a o-ring to go.

The black piece is made of steel, at first I thought that it has some kind of tappered thread, you know, like brass fittings etc.. But it has not, it simply screwes all the way to the bottom.

Jaxx wrote: ↑

Sun Jun 21, 2020 11:01 pm

The black piece is made of steel, at first I thought that it has some kind of tappered thread, you know, like brass fittings etc.. But it has not, it simply screwes all the way to the bottom.

Hmmm...steel? Have you confirmed with a magnet? I was thinking it was either aluminum or a reinforced plastic.

There should be some type of seal if both pieces are metal. Can you contact the manufacturer with your question?

I would expect it would leak if it was indeed just metal-to-metal contact at the bottom of the bore.

Sorry - not much help...

I think I'll just use PTFE film tape, just one or two turns, because thread is very thin... I hope that will work.

Tora had this head (although on Stage6 Big Racing 77 alu cylinder, but the head is the same!) on two of his bikes, I wonder how he got away with them regarding water outlet...

Since the head is not painted at all and cylinder just barely, I have sprayed both of them a couple of layers of heat-resistant lacquer:


Some cylinders (as Airsal 80 Sport) come with coolant fitting for connecting stock PHVA carb heating function. This one doesn't and I'm going to use PHVA carb, so I made one...




I've also chamfered the ports... Didn't bother too much with transfer ones and rather took more time on exhaust.


Right now I don't have time nor patience for polishing port interiors, maybe for some other project (btw I wonder how much difference does it really make?)

I usually use the paste to seal pipe threads, but the tape may work fine.

Plumbing/pipe threads are tapered so they tighten and seal. Those don't look like they would be.

Just not sure what they expect you to do there.

Yesterday I have removed original cylinder (finally...!) and stock stud bolts. They were indeed thread-locked! It's green, haven't seen thread lock like that before... But at least it's similar strength that blue one so they were quite easy to remove...


Stock bolts are too short, so I've replaced them with Top Performances 115mm and also applied Loctite 243 (blue):


Don't have any photo of new cylinder fitted yet, anyway I've tightened nuts with 15Nm in cross pattern, as I should and checked squish clearance first... Stage6 manual says you don't need to check the squish as it's factory set to 0.8mm, I've mesaured it the usual way, with solder wire and caliper and got 0.72mm at start of the squish band and 0.62mm at the end (that's at cylinder bore)... I don't know, but isn't that a little low? Is my torque wrench faulty or what