JBS 700 Kit on welded 80mm Crank

yep! 30 hrs at the pace of a 628 and the jap 450s are toast boiled or really worn out

Ive got 2 frames, cromoly on way to sort out the second one

engine is apart, the fire ring on the head gasket is cracked, they come from thailand its probably made from an old soup tin by someone earning $2 a week. I don't get the cheap labour racket.

if i take 0.2mm off the top of the piston to 100mm diam I can use the OEM gasket, could be OK without doing that but it looks like the piston comes up 0.5mm further than TDC and its only 0.58 below the top.

you wan chitty gasket ? onry 12 dorra ?

5 cracks like this one, ripped it open to show the ID is really dodgy, the fire ring cracked because there was nothing to support it against the combustion pressure. red circled bit shows a void. pic is as crappy as the gasket

do you think that there's a lesson in there anywhere? what does it say.... :wink: :wink:

for some reason it reminds me of the old saying: if you've got a cheap head get a cheap hat!

regards

Taffy

so bushi, would you say the 700 kit is a go go or a no no? do you think my 02 standard crank would be able to handel it, if not abused.... or stick with the standard internals and do other mods to stay on the safe side?

well for me so far its a go if you are prepared to check everything over really well. all the checking and mucking about is why I bough a berg in the first place so I love it.

the only thing i see as an issue so far is the gasket manufacturer, cometic would be a more reliable source I would think.

the 02? why not give it a go? the difference between trying a 710 and just tuning a 644 is that there are a lot more people and a lot bigger knowledge base for the stock engine. the parts for the stock setup are a little cheaper and easier/faster to get hold of.

if you could lighten the 82mm crank it to around 4.2kg it would reduce a lot of the laod on the mains Just my 12c

tried a JBS Multi Layered steel headgasket. it didn't last very long either. flattened everything off nicely too. the hard alloy of the head and the ironliner with a thicker hard rolled edge on the ID of an MLS is a no go IMHO.

machined the piston to clear the smaller ID gaskets. have one last 104.5mm gasket to try and break I made a jig to roll the fire ring onto the fibre tighter. if it fails Il make my own MLA (alloy) gaskets. time consuming but so is changing the gaskets all the time.

The Piston to intake Valve clearance with the X-2 cam was a bit tight unless I retarded the cam, had to remachine the pockets in the piston to use "correct" cam timing as the intake pockets gave less clearance than stock, the Exhausts were fine but in both cases the valves are closer to the centre of the piston than the pockets. new pockets in the right spot now.

with the head off a few times I ported it and put in 36mm kibblewhites from the US and 32mm alloy Exhausts from Taffy, one was machined all wonky but managed to fix it up by taking it down to 31.4mm.

trying the 08 cam again for a laugh, Ive changed 100 things all at once so can't say which did what, I can say power has moved up in the revs, midrange power is up and off idle tourque is down, peak tourque is about the same. pretty much all expected from the cam differences and the porting/larger valves.

its more of a blast to ride, i keep getting emails about the 350 katooms getting holeshots and smoking the 450s every katoom lover wants a 350sx it seems..... Poofs.

bushmechanic said:

its more of a blast to ride, i keep getting emails about the 350 katooms getting holeshots and smoking the 450s every katoom lover wants a 350sx it seems..... Poofs.

Click to expand...

:lol:

Bushie are you using JBS studs to hold the head on or the original bolts.
The studs have a finer thread on one end, giving better clamping.

Cheers spanner

bushmechanic said:

The nuts and washers in the head stud kit don’t fit in/on the head. I made them smaller to fit but It would be better to machine the head to keep bigger washers and spread out the load as much as possible.

Click to expand...

im able to clamp it up fine, problem is the gaskets are crappy. the Fibre ones are poorly made and the MLS one is the wrong design being too hard and having a thick rolled edge on the ID between hard iron and hard alloy means in order to seal the thicker rolled edge needs to squash down but it won't because its steel, the iron liner won't squash iether and the head is very hard alloy so nothing squashes up nicely.

gaskets are a let down eveything else is great.

I found that the jbs gasket were from Thailand:

http://www.gasketstogo.com/

old news as far as Damon is concerned....

regards

Taffy

hey yes thanks contiman I even sneakily asked them if they have any 105mm HBG ones about 2 months ago.. no reply

the current JBS fibre one leaks a bit now (8hrs) if the engine gets hot the fire ring is probably cracked like the last one from lack of support underneath it

got a heap of solutions to try, the best I feel is to get an OEM 100mm and cut out the ID bigger and make some jigs to roll a new fire ring on.

other solution that I mentioned a while back is to sandwich a wire ring between 2 sheets of copper or alloy. the idea is that the pressure helps to push the ring further in

I thought i was being clever till I found these...



and a video of how they make the groove with a pizza cutter rolling disc

http://www.onedirt.com/tech-stories/eng ... e-gaskets/

the guy mentions the problem with this idea and with the MLS is you put a fairly ridgid ring around the bore that needs to be squashed real hard to work and it does but problem with only 4 bolts on a big head is to get the water passages to seal, what happens with copper or alloy is the head bends becasue the ring is thick and the head bolts can only be tightened till the gasket is tight around the head bolts so there are leaks at the water passages between the bolts. in my bike with an MLS it is at the extreme rear, front and RHS of the head midway between the bolts where the head doesn't come down enough. with a fibre gasket the head can come down more at the bolts and then seals off better at the water passages midway between the bolts.

so with a solid gasket you can cover the gasket in wonder goo and hope for the best or perhaps machine out a groove in the block and the head to take a bead of sealant, apply liberally tourque to 30n.m leave over night and tourque again. basically making your own fibre gasket out of a solid core and goo for the fibre, the OEM has a steel core.

the other thing that can be improved is that the water passages in the head are huge and very close to the bore, I can fill them in and re drill the water passages to align properly with the block and be a good 4mm further from the combustion pressure. the ones at the rear (carb side) can even be just left filled right in. the head is made from the same basic casting as the early bergs and the KTM RFS head and they need all the passages open I think becasue of their 1/2 speed water pump.

taking this idea to the extreme i could fill the water passages in the head and the block then run 4 U pipes from the side of the block to the side of the head making it a full closed deck with the water sealing done well away from the liner

its a solvable problem and doesn't bother me too much im just riding it when I can cause its so much fun. The engine works beautifully does just about everything I want and the suspension is sensational I can only complain about teh gumby tank/frame and not enough front wheel trail.

Otherwise, it remains a solution to make gaskets from cometic...

Moreover,
if it works very well with the 700, I'd like to see how it rolls with the 735 or 750!
This should be awesome !!!!! :bounce:

But Ben does not want me to sell the 735 or 750 :cuss:

my 628 untuned is quicker than the 700. all it has is DVSK and cut seats as well as a jetting kit ands it is quicker. the 700 produces more torque but then falls flat I'm told.

so please lads.....save it, come on!

regards

Taffy

I have only used a metallic ring together with a copper gasket on air cooled machinery. I machined a groove in the edge (sealing surface) of the steel sleeve, appr. 0,9 mm deep and 1,0 mm wide. In the groove I placed a 1,0mm dia stainless steel wire. On top of that a water cut copper gasket, heat treated to make it soft. I used this method on my Yamaha TT600 (690cc, 1:12,5, 70 RWHP) with success. Maybe some "bond" can seal the water channels, or instant glue rubber o-rings "inside" the (larger than normally) holes in the copper gasket?

Ah, phuck it! I cannot give bush mechanic tips to a bush mechanic!

Goods tips Dr-C I don't know anything about headgaskets they usually just work but then they are usually made nicely too :? you're right the MLS or your ring trick with copper would probably work well with some goo to help seal the water off or the MLS with a softer core than the solid steel. Ive got hold of some copper, soft alloy and some stainless wire but the water cutter? thats posh 8) I made an alloy gasket yesterday with a lil wood router freehand

Taffy you must have a special old drum of avgas labled "crypt kicker 5" for your 628 which head? whats the CR? the 37/32 head and an x-1 ?

with the stock head (35/30) and the x-2 cam the 700 was a little flat up top, now ported and with 36/32 with the 08 cam the top end works well but the bottom and mid are so strong and responsive the top end is a bit redundant for what i'm doing, it cranks up there but i don't really need to rev it so i'll try the X-2 again and see. I think a little more lobe seperation on the X2 would be nice to spread things out a tad.

with the 628 I had to rev it to get anywhere sometimes and that made me cringe for the mains I feel the 700 should last longer than the 628 in my applciation purely becasue there are less revs on average

be interesting to try my lightweight elko with a Ti pin under this head, then i could lighten the crank a tad as well.

the 108mm bore contiman I reckon would be fine if you don't rev it much and filled the water passages in the head and used a quality fibre gasket. RE cometic USA, they won't reply to my inquiries, I could call but if they're not interested Phuck em. there is a UK branch but I reckon I'll be able to sort it in the shed with a hammer before I got anywhere with them. find out how much the 108mm piston weighs that will tell you how much weight you need to add to the crank and if its worth doing.

so far learn't two useful things: if the headgasket leaks it usually goes where the water passages in the head are closest to the bore and thats on the RHS so the air bleed port area of the head catches some of the gas, great way to check if thats the problem and a big bonus the finned iron liner makes the engine run cooler than the stock one.

why does a 450 beat a 700 in supermono? why does a 450 win in supermoto? why is a 125 now 4 seconds a lap quicker around Donington Park than the woolongong wonder was in 1987?

Imagine it, Jeremy Bradley on a 125 Aprilia V Wayne Gardner and he lets Wayne get halfway to Redgate before leaving the line.....amazing!

the answer my dear Watson is simple...thrash the phucking nuts off the 628 and there is no way!!!!! you can do that to the 700.

regards

Taffy

so would you build them a 550?

for roadracing and sidecars I kind of see the point in a screamer if its for racing

but I'm faster on the 700, funriding and sand MX

more off idle tourque

more peak tourque

less fussy about throttle opening

less gear changes and less clutch work - easier to ride

if i go the other way to a jap 450 I end up killing the clutch and having to replace the piston after 30 Hrs

that said I think a real lightweight build 628 engine with the right cam and this porting/valves would be very interesting, the 105mm piston is 328gm and while not heavy by piston standards its still 20% heavier than the 100mm elko but only gives 10% more ccs.

would I build a 550? well I discussed this with stephan. we worked it out but to get the compression up you need a domed piston so I would defo go to 102/105 to help that. you really want a flat piston.

fact is though that the 628 can reach it's best mean piston speed easily so anything that interferes with that is out. it can reach it and maintain it. it;'s a very good engine. the people beating it have twice the budget (hendrix's of belgium) or the zabel or are simply better riders. as a relatively standard mototr the husaberg is the business.

you do realise nobody with a BIG budget and the KNOWLEDGE has ever raced a Husaberg? the next team has always had MORE.

regards

Taffy

Bushie you might like to give this guy a try,

http://www.coppergaskets.com.au/

pretty sure he could do fire rings.

I inquired about MX composite rod for the 628 but they only have them for the 644 and were not interested in opening
one out.
I am not keen on increasing the weight of any part.
Not sold on large bores either problem with flame speed sealing as you know etc .

Cheers spanner