Hitchcocks Forum

Hi All,

I'm a student in Cornwall and love having my 2004 bullet (500cc) to get out and about the county on. However, since I took the thing abroad a couple of years ago - its never been the same.

I had a burnt out valve which obviously caused complete compression loss, and for the valve to recede into the seat and try to destroy everything around it. When i eventually got it back home (after taking the Hook of Holland ferry to Harwich (overnight) and navigating M25 at rush hour with an engine incapable of idling and impossible to start once stalled without rod-adjustment in standing traffic) I took the head off and ended up having new seat, guide and standard valve replaced and pushed in. Since then, I've had to take the head off another 3 times to grind the exhaust valve back in. Each time it was after a longer 100 mile or so journey. It seems fine with pottering around but i bought the bike because I wasn't afraid of taking it apart and I knew that if looked after, the detuned engine should go on and on! But that much maintenance every 300-500 miles or so is stupid!

The spark plug isn't showing signs of overheating or too lean a burn. Usually comes out with a bit of coke crusting but i often only use it for shorter journeys. The timing might be out but the idle when repaired is usually very good but even with it a bit out - would it cause so much damage so quickly?

I've read on these forums that an oversized valve is sometimes needed with the 500 bullets from India because the smaller valve doesn't have the surface area to form a good seal and so recedes quickly into the head when hot...this certainly happens on mine. Could this be the underlying issue...

Any thoughts on this would be very much appreciated!

Many thanks and best wishes!

Mikey

Hiya Mikey. That's a lot of info to take in there, chum. Would I be correct in saying you believe the valve is burning out continuously, hence the need for a head-off operation? If so, you do have an issue as you should last longer than 100 miles!! Steve

I`ll stick my neck out and suspect you have a weak top end mixture.

Hi, thanks for the replies and yeh - sorry its a lot of info hah! ------ The head keeps needing to come off because the engine looses compression and the push rods need adjusting to be able to start the engine at all. This obviously translates to valve burning/pitting which damages the seal and allows the pressure out (to my understanding). The spark plug as i say doesn't show signs of the mixture being lean... is it worth a bigger jet regardless? Has anyone plumbed for the over-sized valve and found it works? -----cheers! -------PS I've recently sorted the exhaust out which had been leaking air and vibrating in the head exhaust port which i had thought was the issue before - its now airtight and I did a trip to Southampton with girlfriend on the back and a bit of luggage and compression had gone by Exeter (from Falmouth)....so its not a problem with the exhaust pipe.... thanks again.

I'd be getting a better quality valve, something is wrong, they don't normally give this sort of trouble

Continuous exhaust valave push rod adjustment indicates serious valve seat recession........Running an engine with exhaust valve standing off will erode the seat even farther and knacker the valve......... This is all very strange as the valve seat has allegedly been replaced and all the more so as we are discussing a 2004 made machine..........I have had exhaust valve problems as described and the seat recession was measurable with a depth gauge!!!!....But the Infamous Bullet is 1992 with soft seats not 2004 which should have hardened seats ...........I had the seat replaced by a reputable specialist precision engineering company who matched the seat to the Hitchcock supplied valve......... After 10s of thousands of miles no further problem.........As there is a free flowing exhaust fitted the carburation has been richened to compensate..........I am wondering if whoever did the head work merely re-cut the existing seat?????????...........Just my thoughts and my 2 drachma

Morning Mikey. I think there's a common theme appearing here now! If funds allow, get a secondhand head & new valves, if not, try a good specialist and effect a repair with name brand valves. It's definitely down to poor materials and/or poor repair work. Running a larger jet will just mean higher fuel consumption, so if you have repair work done and you'd feel happier then by all means stick a slightly larger jet in for a while. Good luck & let us all know!

being a student money will not be plentiful, so may be try a different tack for a while.........Tidy the valve & seat by grinding... buy a bottle of Castrol Valvemaster & add to petrol now and at every fill up erring on the side of slightly more than less...........another of my 2 drachma!

Mikey,
Check the valve seat and make sure it is not turning round, i had the same problem and i only noticed it because a shiney bit suddenly showed up on the seat after i lost all compression. New seat and new valve and no problem since.

Thanks for the comments guys! ----- You're right about student money not being plentiful! When I had the new guide, seat and valve put in, I bought them from Hitchcocks - the seat was the EU quality - the valve was the standard Indian replacement and the guide was a standard (UK made i think) original size. I'll check if there's any movement in the seat... its now got a large lip on the inside where the valve has shrunk in. Often its not so much the valve burning out itself but the damage caused to the seat which I think starts the process. ----What will the Castrol Valvemaster stuff do?--- Looking at buying a new high grade seat, oversized valve and checking the guide when I take the thing apart in a few days time. I'm guessing there's no point in just buying a large valve if the seat is suspect too...? ---- the other thing as Beezabryan mentioned - the exhaust I did change for the short Indian type which I believe to be freer flowing. This was done recently (before the most recent problems) so I'm guessing it can't hurt to try a larger main(?) jet? ------ Anyway - appreciating the feedback! Thanks again!