Nikasil Aluminum cylinders from Molnar

Very happy with the 750 Maney alum barrels I'm using. 920 owners might want to change out the soft SS through bolts for higher grade reduced shank bolts. I know of a racer that had his softer SS bolts fail.

jseng1 said:

Very happy with the 750 Maney alum barrels I'm using. 920 owners might want to change out the soft SS through bolts for higher grade reduced shank bolts. I know of a racer that had his softer SS bolts fail.

Click to expand...

Jim, were those stainless through bolts from Maney? All the cylinders I got from him (5 or 6 in total) used normal high strength socket head steel cap screws, not stainless. The only one I ever built using stainless bolts was an ultra short stroke 750 with a shorter cylinder requiring custom bolts. I used reduced shank ARP stainless bolts, and you certainly couldn't call them soft. Maybe Steve changed in his later kits? Or maybe the racer you mentioned decided to use some other bolts for appearance's sake?

Ken

I think Steve must have changed his bolts Ken, my 920 came with stainless Allen bolts. Whether they are ‘soft’ or not I couldn’t say as I fitted reduced shank ARP bolts thanks to a mate called Ken in the USA !

I had stainless steel head bolts from RGM. The head leaked as they stretched. When Steve did some work on my bike he said they were the wrong grade of stainless & he remade them. So no, I would say that its not the case! Steve was aware of the requirements.

If I remember correctly the bolts Steve supplied on both my sets of barrels were A4 grade which is 316 stainless. 316 has a similar tensile strength to a 8.8 grade HT bolt. Most of the stainless bolts supplied for classic bike purposes are either A2 which is 304 or 303 free cutting. 303 is in my opinion not suitable for head bolts, wheels spindles etc.

Hi , to check if 316 or 304 , 316 is non magnetic 304 is tiny ferritic ( will attract the magnet a bit ) but could take slight rust pitting , on my alloy barrel I had fitted SS ARP bolt which is said to have 170 000 psi strenght , but dunno if it's tensile or yield strenght ???? what's your thoughts ...........

marinatlas said:

Hi , to check if 316 or 304 , 316 is non magnetic 304 is tiny ferritic ( will attract the magnet a bit ) but could take slight rust pitting , on my alloy barrel I had fitted SS ARP bolt which is said to have 170 000 psi strenght , but dunno if it's tensile or yield strenght ???? what's your thoughts ...........

Click to expand...

It's tensile strength.

Ken

Tensile strength of 304 or 316 bolts is usually in the 70,000 to 80,000 psi range. ARP stainless bolts are in the 180,000 range. I prefer genuine ARP bolts and reduce the shanks so they stretch instead of loosening or pulling out threads. Below is a failure photo of non- ARP stainless bolts.



Machining the ARP bolt shanks along the linear axis so they are fluted avoids stress risers and increases twist resistance (while torquing down) compared to smaller diameter reduced shank bolts. Anyone can do this with a good CNC mill or a lot of patience with a Manual mill. Fluted cylinder through bolts cut on CNC mill below.

Hello and good afternoon from Germany,
well, I had a Maney cylinder barrel. The bore was 79mm, as far as I can remember. I also got it Nicasil- plated from SMA- Racing in Germany. As they are more experienced in single cylinder racing (Matchless G50), they recommended a piston to cylinder clearance of 0,03- 0,04mm (with custom made Mahle pistons). No, I said that would certainly too little for a twin and ordered a clearance of 0,06mm. When I received the whole set- up I measured 0,10mm , which would have been too big. Anyway I never got it really running because of certain other issues.
What gave me the biggest headache was the fact that I never got a really well sealed cylinder head gasket. I always opted to copper gaskets, which would give the best heat transfer between the cylinder head and the barrel, apart from Jim's solution. Anyway, I gave it up and went back to the standard cast iron, which is certainly only the second- best solution. After all, the engine was always intended to be ridden on the road.
I suspect that due to the open cylinder bolts the cylinder was always distorted.
So, to me the Molnar cylinder barrel (theoratically) has its biggest advantage with through - bolts completely inclosed into the casting. A distortion seems to be reduced to an absolute minimum with this solution. This is the biggest advantage of the Molnar solutuion.
Now to the Nicasil- coating: The cast iron liners have a completely different thermal expansion in comparison to aluminium. I have seen Dunstall cylinder barrels with cracked liners in the area of the head gasket. The reason being that the liner was pulled downwords into the crank case resulting in the cracked liner. This again can result in liners pulled down into the crank case by the piston rings while the engine is running (A complete desaster, happening to Roger Titchmarsh with his 500cc Nourish Weslake). The solution is, that the liner has an interference fit so that it can partially move within the cylinder barrel. This certainly cannot be an ideal solution, because due to capillary action oil will creep in between the barrel and the liner. So, the heat transfer between the liners and the barrel is interrupted. I know that Honda and most of he Japanese manufacturers had this solution. But to me, the best solution is the Nicasil- plated cylinder.
Another word to thermal expansion. The problem is definately not the expansion as such, but the different expansions between aluminium and cast iron (different materials). So with an cast iron cylinder the cylinder head, the cylinder barrel and even the crankcase are working against each other instead of working together. So, even here we have a big advantage of aluminium barrels (and not only the lighter weight and the better heat transfer).
That's my thinking about the Molnar cylinder barrel. I would try it but, being a pensioner the financial resources are rather tight.
Best Regards
Klaus

Klaus

You could have your pistons coated with graphite at "line 2 line". You could coat them to any clearance you want.

I think Maney used only .0005" interference fit with his iron liners in alum barrels.

Andy is considering the 81mm Nycasil/aluminum bore. I suggested he angle the through bolts slightly so they give 1mm more clearance at the top near the bolt counter bores. They should still thread in no problem (just an idea so far). If anyone's interested in a Nikasil 920 now is the time to contact Andy. No one is making 81mm alum barrels now and he just might.

jseng1 said:

Andy is considering the 81mm Nycasil/aluminum bore. I suggested he angle the through bolts slightly so they give 1mm more clearance at the top near the bolt counter bores. They should still thread in no problem (just an idea so far). If anyone's interested in a Nikasil 920 now is the time to contact Andy. No one is making 81mm alum barrels now and he just might.

Click to expand...

Just spoke to Andy and he's got castings coming in 'in the next week or so' and is assessing demand, so now is definitely the time to get in touch.

All you need to do is change the fuel rules to permit use of methanol and most of the problems become simply academic. Cast iron barrels on Commandos work well with methanol. If you used aluminium with Nikasil bores, you have the problem of getting the motor hot enough, so you don't hammer the bores. The Commando motor on methanol is usually fast enough to be competitive against most large four cylinder bikes. And you probably would not bother to run a big four cylinder bike on methanol, or you can fiddle the rules to stop that from happening.

If I had to go over 900cc to remain competitive with a Commando, I would find something else to race. In Australia, we had 'sounds of singles' with no upper capacity limit. To stay competitive, you needed the 650cc single. That race class is now defunct. All the big motors blew up too often.

Methanol, what a good idea. Next time I'm out for a thrash I'll go to the petrol station, give the super unleaded a miss, & fill up up with meth.......... ang on, what do yer mean yer don't sell it. Well I never!

Matchless said:

Methanol, what a good idea. Next time I'm out for a thrash I'll go to the petrol station, give the super unleaded a miss, & fill up up with meth.......... ang on, what do yer mean yer don't sell it. Well I never!

Click to expand...

You don't need a race motor in a road bike.

acotrel said:

You don't need a race motor in a road bike.

Click to expand...

Life is full of things we don't really "need". That doesn't mean we shouldn't have and enjoy them.

Ken

If this forum was all about 'need' it would be a dull place!

I will have to ask the club to change their rules so that I can run on methanol. Mind you while I'm at it I will ask if they can pay my entry fees as well.

Chris said:

I will have to ask the club to change their rules so that I can run on methanol. Mind you while I'm at it I will ask if they can pay my entry fees as well.

Click to expand...

And just throw away the rule book so that any old POS can cheat , do away with all the traditional/proper classes too