Forum

[stinkwheel]

I'd hesitate to suggest a piston, or even suggest that is the root cause of the problem. It was just an observation. Superficially (looking at pictures) the cutouts on the higher compression pistons all seem a little larger in both depth and diameter. This doesn't mean they will have more clearance though because they will also have a larger dome.

[adamscarborough]

Thanks stinkwheel, I don’t think the piston will solve the problem either but if i’m having to enlarge the cut out to be atl least in line with the valve I’m better of starting with a decent quality piston rather than the ugly old thing I have. As bullet whisper has pointed out the valve too close to the piston even before it starts to open but I’m stuck with it, as someone else pointed out you can get spacers to fit under the barrel which will drop the piston to achieve any further increase in clearance that might be still necessary.

[another Allan]

Why do you feel that you are 'stuck' with the large valve?
Has the seat been replaced with a larger diameter one?


If not, would it not be worth trying a standard-sized valve?


As Paul (BW) has pointed out, no benefit has been found in having such a large valve. Therefore, trying to modify a piston to accommodate something that is not beneficial sounds like a bit of a blind alley.


By all means plough your own furrow, but many a wise man has referred to 'standing on the shoulders of giants.'


(Sorry for mixing the metaphors.....)

[another Allan]

No idea where the bold text came from................

[ChrisD]

Hi Adamscarborough and all. I am rebuilding my 1996 535cc which dropped a valve. I too have bought the larger inlet NOS ‘scrambles’ valve (PN 38094A) as the only directly-fitting alternative to the Indian inlet valve, also the larger exhasut valve, Hitchcocks performance cams and their 535cc 8.5:1 piston. Over the past few years, I’ve run into so many problems due to weak, non-fitting c***y indian parts that I am trying to swap out as much OEM stuff as I can with NOS UK stuff as it becomes needed. Hitchcocks advise that valve should be OK even with the larger exhaust valve that I have fitted (PN 90053). However I haven’t got the head fully back together and I suspect that even if there is no obvious clash between the valves, I must check it anyway 'cos I am now worried that I’ll have the same issue. I may buy one of those borescope cameras to check for clearance, one that inserts down a plughole. If that works, I’ll post the video.

BW states that the larger valve has no benefit and his view is well-respected, so I accept that. I may replace it with an indian one if there’s no space to trim 20thou or so off the circumference. If the former, I’ll need a new seat, methinks. Alternatively do you think one could substitute an inlet valve with one of the larger exhaust valves??

Cheers., ChrisD

[Dennis C]

I understand ChrisD wanting to fit non Indian parts, but can anyone tell me any other reason they think the bigger valve is beneficial?.

[Beezabryan]

After an hour or two with the Flash I will go for a ride on our largely unmolested Bullet, after all that is what it was made for