Billet cylinder head

as you said , valves has touch the piston, its clear , it is a problem of clearance or it is a problem of timing , i think you have controled both

it may be a compound of two thing, clearance and valve spring , 100 kg for 66 grams valve looks pretty low ( for me !! )

about clearance, i had some little marks even with 2 mm between piston and valves , to be save i get to 3 mm , and now , no marks at all .

woosner piston under stress can have .3 to .5 mm crown dilatation , it doesnt help also !!

these , are just some ideas to understand whats happens :wink:

Hi DOC

One question for you, much more simple to answer than the one of the valves, could you tell us how did you changed the magnets on the flywheel ? And where did you get the magnets ?

That shure will help the ones that still are using this engines.

Thanks and keep going You will get there

:cheers:
ZAGA

Mats,
I feel for you. A thoroughly bad run of luck. Racing just wouldn't be the same without such disasters though, so don't give in!!

Just watched your video and I noted your frustration on the iridium spark plugs. I'm intrigued! Combustion & ignition research is my day job in the real world and I've designed many a spark plug in my time, so I'd love to get to the bottom of your ignition woes.

If you tell me which iridium spark plugs you were using, what you used to replace them, your coil characteristics, your compression ratio and your approximate ignition angle, I'll run some calculations. There'll be a whole bunch of estimation required unless you know stuff like the local mixture velocity in the region of the plug electrodes at the time of ignition, but I'm reasonably sure we'll find the spark migrates away from the spark gap at high engine speed, probably flashing inside the spark plug shell. Ordinarily this massively compromises the ignition capability of the plug, either resulting in a complete misfire, or at best slowing combustion to the point where you'll get a partial-burn and a sudden need for massive ignition advance.

If you can send me the plugs you threw across the workshop (assuming they're still OK), I'll even run them in a dynamic engine simulator that can create pictures like this:



... and tell us what's going on.

Overall firing-end configuration, spark gap size, electrode shape and temperature, orientation of the ground electrode relative to the flow, peak spark current, spark duration, fuel type, mixture strength and quite a few other aspects affect the resultant spark performance. The ideal situation is as shown in the picture... and Iridium electrodes can do interesting things at high ignition pressures which certainly do not give you an ideal discharge.

I'd be happy to help if you want to find the answer, and frankly speaking, it would be interesting for me too.

Let me know.

Cheers and regards... Paul

Hi all!
I have fulfilled 5-6 dyno sessions (appr. 50-60 full throttle runs in total) with this build, revving up to 9200rpm. No signs of contact between valves and piston during that period (split the engine 2-3 times). Checked piston to valve clearance when I put it all together and left it with 2,0-2,5mm axially and 1,5-2,0mm radially on the intakes. Appr. 0,5mm less clearance on the exhaust side.

On my old Yamaha, I had to use at least 1,0mm in squish clearance. With 0,9mm squish the soot was gone! The elongation of conrod, flexing of crank shaft, deformation and tilting of piston sure adds up. Especially with large stroke and rpm. On this engine the squish clearance is 1,0-1,1mm.

The springs are a bit on the weak side, but the cam profile, valve train inertia and rpm decides wether this will become a problem. The Husaberg cam profiles are tough on the valve train and especially the roller bearings, as you all know. My cam profiles are custom made and working directly on tappets. The valve springs do not have to move rocker arms with whatever inertia they are contributing with. The logging during the trianing sessions showed that I was never over 8500rpm. I put my money on the timing being off for some reason. Maybe the cam sprocket has moved on the cam shaft again?

Yes Taffy, the piston ring remains are on top of the piston. If you saw the cylinder sleeve you wouldn't wonder why...

@zaga: I'm not sure getting hold of new magnet rings is simpler than the other questions! My fly wheels are a prototype SEM made for the Cannondale project. A former SEM employee happened to have 2 rings on the shelf. I just glued them on place with a high temp version of Araldite. I have stressed him on getting info on what company provided the magnet rings, but both times he avoided the topic with words like: difficult, expensive, need large volumes, and so on...

@Paul: Thank you very much for the offer! I will contact you directly for you address. I'd be happy to send the Denso IXU24 and IXU27 as far away from my shop as possible. France will do. I have had these plugs playing tricks on me both with my previous head and this one. The rpm when it misfires has varied from time to time (6,5-8,7k). Load (TPS) doesn't seem to affect the misfiring noticeably. Fuel is Shell V-Power which should be 100 octane. Geometric compression ratio is 14,4-14,7:1 When switching to a well used NGK DCPR9EV the misfiring stopped. I put in a new NGK DCP9E with 0,8mm gap for the races, which had some slight misfiring tendencies also. After adjusting gap to 0,5mm that was cured for 2 laps, then the gap was adjusted to 0mm by the engine itself... :wink:

Hi DOC

Thanks for the info, it was great if you had some kind of solution, as Paul allready pointed out several times, the magnetic force of the flywheel will play a major role on the output of the stator. And in the near future will be a problem to most of us.

One advice, you take the opportunity of having F1 consulting for free with Paul.

:cheers:
ZAGA

I don't know whether to read that as a go at me or not?

If I'd known for a long while I'd have let you know that they didn't work.

strange world.

perhaps I need to race a 650 on the roads and until then shut up?

regards

Taffy

Taffy said:

I don't know whether to read that as a go at me or not?

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Not. Puzzles me how you even came into that thought?

well I sold you the plug, I sell the plug proclaiming how good it is, I proclaim the plug answering all querries here.

look around first?

regards

Taffy

Valve springs stomping in their seats because of harmonics in combination with low closed valve spring force? Even when the tappets should be following with that force. Mysterious....

This isnt really of much assistance, but I installed iridium plugs into a chev LS1 engine in a road car and immediately replaced them with oem spec plugs because of a misfire. I not having a crack at anyone by the way.

Smorgasbord said:

Valve springs stomping in their seats because of harmonics in combination with low closed valve spring force? Even when the tappets should be following with that force. Mysterious....

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I agree with you 25 kg is a very low number , for that kind a valves from 40 to 60 grs I never get bellow 35/40, kg , with or without rokers , harmonics in reality can make strange surprises ,far from calculation, I had experience that :?

and you'll see it on track , not on the dyno , the engine doesnt revs the same , stange that also , but real :wink:

I would like tougher springs, no need to convince me on that topic. . Perhaps the community can help directing me towards good suppliers or other OEM-products that might work?
The installed height for the outer spring is 36,0 mm, max OD for the spring is 28 mm and max lift 13 mm.

Dr_C said:

... left it with 2,0-2,5mm axially and 1,5-2,0mm radially on the intakes. Appr. 0,5mm less clearance on the exhaust side.

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Sorry! It was the other way around! Larger clearance on the exhausts of course.

I have sent R&D springs a request. You guys know other spring resources?

Kibblewaite

as I understood it there is a theoretical difference between OHC and DOHC in the way a valve is opened. I'd have thought:

revs
weight of valve
DOHC application

you're there.

Ferrea?

Taffy

there is no many room for a spring out there !! :?

anyway in case you can do some milling job , get to PAC racing springs in US there have very good stuff , I personnaly use the Beehive spring the PAC 1523 , no rebound , no failure , no troubles at all :wink:

I rev up to 9500 k , and I have rockers on my Ktm 690 engines witch is a bit worth to move :?

oem stuff is for oem use , your engine is far from that , i had the same problems with my engines , care with R&D springs I report some failure , Kibblewhite is a good supplier for stock use ,I dont know the reliability in hard use
Ferrea has a good experience in racing to ,even if I had some failure with theyre TI valves , that time my springs were too soft :?

:wink:

Good tip, FDracing!
PAC seemed to have a good selection for racing use. I have written them a mail with my specs.

I was at the work shop today. The cam sprocket is positioned exactly where I left it (LC=108). I fixed the cam in the vice and tried to turn the cam sprocket. It is not moving one bit. The valve springs are moving up towards the "prime suspect" position. ;-) "Funny" how the engine can have lived through 50-60 full throttle runs at the dyno, and packs up after 5-7 laps on the track. :?:

Dr_C said:

"Funny" how the engine can have lived through 50-60 full throttle runs at the dyno, and packs up after 5-7 laps on the track. :?:

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after many years and more than 400 dyno runs , I report 2 engine failure on the dyno , all the "breakage" I had were on the track , an engine really works there .

failure is the first step of understanding , is the real way to learn the how and the why , especialy in engine racing , and singles cylinders are the tuff one , exactly as the guys who worked on them :wink:

fdracing said:

..and singles cylinders are the tuff one , exactly as the guys who worked on them :wink:

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I hear ya... ;-)
Today I ordered some PAC-1523 springs. They would give me 53kg seated (36mm) and 122kg at max lift (23mm). The seating pressure seemed a bit over the top, so I asked them to grind them a little more. That will end up with 45kg seated. This will hopefully be closer to what you would think is normal for this application.

The winter coma has finally lost it's grip. Valve springs have arrived. 8 valve blanks have arrived and been adjusted in the lathe. Valve guides are also in the house. The damaged head is welded up and both heads are at "Topplocksverkstan" to get seats, guides, porting and nice combustion chambers. I made a couple of nice battery boxes and now some carbon fibre work for a cover to the EFI to keep it from the rear wheel splash. I have laid my hands on a 35mm pin crank. One more would be good. Anyone having something for sale? As piston and sleeve also died when the valve broke off, I'm thinking of a larger steel sleeve and a new piston.. Next one up is manufacturing new valve spring retainers to go with the new springs. Aaaah... good to be active again!

I do a 35mm pin and it is from Alphas so you can gaurantee the quality!

boring them out is so ify Mats....102mm is all I've heard of being completely reliable although I gather head gaskets have a fair bit to do with it?

Taffy