worn valve guides

spanner · Jun 29, 2008

I am doing a 100 hour rebuild of the top end replacing cam chain, valves, valve guides, valve springs( KTM 450 springs) and a reground cam, If i can chose a profile! etc.
One thing I have noticed is that inlet valve guides are very worn at the rocker end, probably 2-3 times as bad as the exhaust guides.
I am suspecting that the rocker arm geometry is different on the inlet side compared to the exhaust.
With a higher lift cam this could become worst.
Unless longer valves are used.
Has anyone else noticed this.
It is the 05 model.
Cheers Spanner.

Taffy · Jun 30, 2008

the race cams only lift 0.5mm more which on a scale of 12mm is not much i think you'll agree. also the race cam such as the LX1 and LX2 are softer on all the valve gear.

i nearly started a thread the other day just to compliment husaberg on their guides because i haven't heard of anyone needing any! oh well.....always a first time!

regards

Taffy

ned37 · Jun 30, 2008

fwiw, i was inspecting the 02 650 last month and decided to have a look inside the cylinder using a flexible scope and litesource i scored from the hospital i used to work for. when i was viewing forward to the left, i saw this huge dark area and thought it was the cylinder lining coming apart 8O until i got close and realized it was oil drool coming from the left exhaust guide! evidently, after it's parked on the sidestand for awhile, it drains into the cylinder. the bike doesn't show any signs of smoking on startup or after long decel, so i don't worry about it.

spanner · Jun 30, 2008

Inlet guides measure 6.4 and 6.5 at the seal end (roughly with vernier) I did a quick trial assembly without valve springs, and watched the rocker arm adjustment screw and how it related to the axis of the valve stem whilst rotating the cam. They don`t look ideal but is hard to tell with the foot on the adjuster.The exhaust side looked better.
Taffy, if the geometry is wrong to start with it could be even worst the higher the lift of a LX1/2 as the adjustment screw is traveling in an arc and the further it moves off centre to the axis of the valve stem the more side lode on the valve stem therefore more wear on the guide. This is how I understand it. I think I will have to take the foot off one of the adjusting screws and make a lash cap to replace the hight of the foot then I would be able to observe the movement of the ball end of the adjusting screw in relation the axis of the valve. It should travel the same amount each side of the centre line of the valve during the valve opening cycle.OR should it be on centre at full lift when the maximum spring pressure is on the assembly??? will have to do some research.
I have ordered some valves that are longer than the Husabergs so I will have the option of making them longer to the extent of how far I can back off the adjusting screws, about 2mm by the looks of it.

Welcome to any opinions ,
Cheers spanner.

spanner · Jun 30, 2008

Ned, I pulled the head off because I noticed very fine metal when I last changed the oil it looked like brass and I now know where it came from I first thought it was aluminium and the oil was tinting it a gold colour there were a few bigger aluminium particle's I think came from where the cam chain had started to rub. No steel to speak of has been on the magnet yet. The valve seals would probably stop too much oil getting down the guide, mine still feel reasonable on the stem, even though the guide is flogged out.

spanner.

Taffy · Jun 30, 2008

spanner

it's vital that the pressure is off-centre when there is maximum guidance and contact twixt valve and stem and by the time the valve is on full leverage and the guide at the far end of the valve it should be a neutral push.

as i said before, i think the guides are the only thing on these bikes we haven't even had to worry about! they've been spot on!

as for neds leak well ned we can't blame a guide for an oil leak can we? surely it's the VGOS.

VGOS lose their suppleness as they get older so.... and compare the prices:

VG's and valve seats cut plus seals

or

try just the VGOS.

regards

Taffy

ned37 · Jun 30, 2008

when i rebuilt my 70's triumph trident, one of the mods everybody did was to add oil seals to the guides. only place anybody used them was the intakes because the exhaust being under pressure wasn't going to suck any oil in.

spanner · Jun 30, 2008

My new guides just arrived, the inlets are 4mm shorter than the exhaust, looks like I will be ordering two more exhaust guides to put on the inlet side.

spanner

worn valve guides

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