Hitchcocks Forum

decided to have a nice steady ride out to matlock bath yesterday evening. the 500 bullet (4 speed box etc) was going well after the nipping up on Saturday. got a few miles and the exhaust started to make a very weird noise along with a clattering sound on the over run, but fine under power. got 6 miles, pulled up at a junction and she just died. no compression. still none this morning, so its not a heat thing. Got it home eventually (long story, the RAC are c**ts).

it turns over, there is no compression, the exhaust emits a light 'huff' but there is a mechanical clonk, for the sake of a better word, every time it turns over.

any ideas? holed piston? detached piston crown? broken exhaust valve? all suggestions welcome before I get the spanners out, which wont be till tomorrow night at the earliest.

After the event I know, but stopping straight away with ANY unusual noise from an engine and getting trailered back home is cheaper than an engine rebuild.
(It too me years to stop my wife "soldiering on" when some kind of knick knack knocking sound appeared instead of stopping and calling it a day.)

Hi, if the engine emits a huff then doubt its holed piston as its still pushing air. check exhaust valve train. possibly stuck valve (hence lose pushrod clattering) or something holding valve open. Was it hot weather when you were riding? Valve tend to stick when bike slows not when power is on. Was there a backfire prior to stopping?

Yes it was damn hot! no back fire that I heard ..

if it is a stuck valve.. any one else had this problem? will it need a new valve? will the guide be knackered too?

It might be a loose valve seat - see my post about one not too far down from here. Cheers, Paul.

same here-ish,



My inlet valve sticks open when idling or slow running not under power. often, there is a backfire through the carb, blowing it off the engine and rotating it and the tea caddy (air filterbox) backwards, then there is no compression.



yours sound like it may have got damaged, but mine sticks (gone in to be fixed along with general engine strip now). I found that by guessing TDC by where the wheeze out of exhaust was, I could open the throttle and kick, with the engine starting. Must have been enough of an explosion to unstick the valve and bang it shut.



It's trying to tell you that it needs attention. Sooth it with some spanners, and with maybe a new part or two, it'll be reassured and should run better.

HOW IS THE VALVE GUIDE KEPT IN? PUSH FIT?

These notes under the technical note section on left will come in handy for you just copy & paste link.
http://www.hitchcocksmotorcycles.com/pi ... bullet.pdf

pd110961 Our hosts do a valve guide removal and insertion tool:-

Scroll down the page:-



http://www.hitchcocksmotorcycles.com/ac ... ols-engine