Mistery Hole?

JBSracing · Jan 13, 2005

Hello every one.

I have been looking at the head in the 650/750 conversion Husaberg today and have noticed a hole drilled from the outer edge of the head on the sparkplug side through into the spark plug recess!

As far as I can see its just for drainage, can anyone confirm this?

The reason that I ask is that I am considering the possibility of setting the head up on a mill and sinking a slot drill through so that it runs from the top outer edge of the head and cuts the web that the hole is in and comes out next to the valves on that side. This hole would then be filled with tight fitting plug of aluminium all the way through and welded both sides. Then drilled and taped for a second spark plug. I have done this on a KX 500 head and it worked well, Zabel and MTH sidecar engines both have twin plugs. It seems to allow more flexibility and less sensitivity to carb' set up and better overall performance.

Any thoughts on this as an idea??

kez · Jan 13, 2005

JBSracing said:
Hello every one.

I have been looking at the head in the 650/750 conversion Husaberg today and have noticed a hole drilled from the outer edge of the head on the sparkplug side through into the spark plug recess!

As far as I can see its just for drainage, can anyone confirm this?

The reason that I ask is that I am considering the possibility of setting the head up on a mill and sinking a slot drill through so that it runs from the top outer edge of the head and cuts the web that the hole is in and comes out next to the valves on that side. This hole would then be filled with tight fitting plug of aluminium all the way through and welded both sides. Then drilled and taped for a second spark plug. I have done this on a KX 500 head and it worked well, Zabel and MTH sidecar engines both have twin plugs. It seems to allow more flexibility and less sensitivity to carb' set up and better overall performance.

Any thoughts on this as an idea??

It Is A Drainage Hole Used To Allow Water To Escape From The HT Cap.
If It Wasnt There The Water Would Get Trapped Under The Cap,Turn To Steam,Popping Off The Cap In The Process.
Best To Leave It In There I Think?

JBSracing · Jan 13, 2005

Thanks for confirming its water drainage. I'd re-drill the hole afterwards the water would flow out of the top hole through the second hole and out.

Is that reasonable do you think?

Any technical opinions on weather its worth having the second plug?

Thanks for the feed back

berger · Jan 13, 2005

I don't know, but I think you at least qualify for vice president of the Husaberg Mad Scientist's Club

Gix · Jan 13, 2005

twin plug head

There is currently a guy who turns up on a husaberg motored supermono road racing bike at out local test track.
His bike runs an 02 650 motor and runs a twin plug AND twin carb set up... don't ask me how he's done it as all I know is the bike blows away standard bergs on a straight...personally I think he needs to get out more, but hey ho, each to their own I guess

LINEAWEAVER · Jan 13, 2005

Hi Ben,
Between big valves and multiple spark plugs you should soon be running out of head.

Seriously, the hole is a late addition as early engines were not equipped with said drain port.

Early models relied on a close fitting rubber flange (attached to the spark plug cap) to keep moisture out. Such did a fair job. Trouble came about when one decided to pressure wash their pride and joy.

Sincerely,
Dale

JBSracing · Jan 14, 2005

Well this sounds positive, I am going to see if I get a third 650 head and give afore mentioned mod a go. It might take a while as I have to get the 750 finished with a stock (ish) head first. But when I do photos will be in my gallery.

I should get the liner from the machine shop soon, photos coming, its not as thin as you might think. In fact the part that takes combustion pressure is never thinner than 4.75mm (in unsupported sections), the only thin bit is at the bottom were the 3 o-rings are on a stock liner it is 1.95mm. I am running no o-rings but am sealing it with a coat of twin pack high temp RTV (they used it on rockets at a place I worked). Hopefully this rubber coat will help to break up vibration/ringing that might be set up as well.

As for the mad scientist comment, guilty as charged. I just love engines and can't resit tinkering with their innards. Last month a friend of mine bought one of these silly 39cc mini-moto road racers (naff) in a week I had persuaded him to give it to me and it is now 52cc, looks stock still but it goes a wee bit better.

Jocke_D · Jan 14, 2005

JBSracing said:
It might take a while as I have to get the 750 finished with a stock (ish) head first. But when I do photos will be in my gallery.

weeeeeeehooooooooooo. I must say you qualify for the 1st chair in the MHS club (MHS = MadHusabergScientist) 8O
A 750cc Berg must be like heaven with a twist.

Can you tell us more about it. Bore x Stroke (am I stupid if I think you are running 114x140??) and all other nice things you have changed on it. I'm hoping this beauty of a beast is going to sit in a supermoto bike. Please ad more photos asap.....

JBSracing · Jan 14, 2005

Hi Jocke_D

The bore is 105mm and the stroke is 86mm, on the 750cc Husaberg that I am building right now.

The engine is going in a Sidecar, see www.sidecarcross.com, I have added a picture of said sidecar to my gallery.

----------------------------------------------------------------------------------

I can see were you got your figures from, in my galley there is a 114mm piston but that is for another engine a 900cc single (not based on a Husaberg) and a 140mm between centres conrod (thats from the centre of the little end lin to the centre of the big end pin).

To work out the cc of an engine you need to know the bore and stroke.

cc = bore x bore x stroke x 0.7855

(if you want cubic centimeters you must put centimeters into the equation, so a 105mm piston = 10.5cm)

So, cc = 10.5 x 10.5 x 8.6 x 0.7855 = 745cc

Other than cc:

The counter balancer is gone
The main bearing are up-rated
The inlet and exhaust are much straighter, bigger, smoother and are tuned and matched to each other.
The carb' is a smooth bore 42mm pumper carb'
The radiator is huge
Oil cooler added
Much head work!

These are the engineering changes now I need to get the 750 running and I can start tuning the system.

If you want one in a supermoto I'm going to sell the kits in the spring once its tested. I am going to do a 710cc kit which uses the standard crank and my 105mm piston, liner and conrod and of course the full 750 with a billet crank.

Best Regards

Ben - MHS
JBSracing

Grok · Feb 13, 2005

Drain hole and handy blow hole!
I always blast air up through the hole after pulling the plug cap, before removing the sparkplug. Very effective for getting any loose crud away from the plug hole and prevent it from dropping in the engine.

Search

Search

Mistery Hole?

JBSracing

kez

JBSracing

berger

Gix

LINEAWEAVER

JBSracing

Jocke_D

JBSracing

Grok

Similar threads

Register CTA

Recent Discussions

Recent Discussions