Hi I had a vertical belt fail which has bent a couple of valves gutted but it could have been a lot worse so while the engine is in bits do I fit some new pistal pistons that I got a while ago if so does that mean that the engine would need to be balanced ? And are they worth the extra expense ,would I really gain anything ? they look like original Pistons not the HC racing items and do say "drop in " but not so sure from what I be read on other forums they are lighter ? Has anyone had some fitted ?
Presumably (if valves damaged) then your piston(s) is beyond use anyway? If so then rather than buy new OEM pistons use these. Probably need to be splitting the cases anyway after a piston to valve collision, so balancing is not much more work at that stage and best done even with standard pistons, once apart?
Sensible option is really to strip the engine and when it's apart get the rods and crankshaft balanced and set the crankshaft end float as tight as you can get it within the correct limits. Might be worth checking and replacing the main bearings as 998's are known to have main bearing problems and I know of at least two personally that have had them fail. If they go then the alternator case will mostly always go with it, even more expense then. I had a 748R engine main bearing go after just 4,000 miles from new. Parts are expensive though and it cost me £950 just for the parts to rebuild my 748R engine plus a new alternator side casing.
the belt that went was the vertical one so only that one needs to be repaired as far as I know the piston is from what I understand but I don't understand what happens when a belt lets go can some one please explaine to me ? As far as I know I don t have replace the Pistons was looking to see if putting these in is worth it as I am on a budget so the cost an issue at the moment
Piston to valve interface doesn't mean you need new pistons.The head will need to come off so you will see the piston and you will be able to see what damage there is to it,if any.Ideally,an engine strip is the best way.I personally ,would have no probs just sorting the valves and putting it back together.As long as the piston has no bits missing.
I was told that all I would need is 2 new valves that's it everything else ok , I think I got away with it really very lucky ,so I can just replace them put it back together and off we go but it s just the engine had been opened and I just happened to have the Pistons which say "drop in " i am just trying to see how much work & £ it would be I guess I was hoping for a bolt off bolt on but not that simple
I don't want too open the bottom end because I don t have the money for such a job but I will double check with my friend tomorrow
Even if the pistons aren't damaged, you'll need to take the head off to swap the valves. Once the head's off the cylinder will be loose and will need to come off for re-sealing, at which point you can remove the piston and weigh it. That way you can decide if the new ones would need balancing or not. Personally I would, at the very least, have both cylinders off to clean up & overhaul the heads then whilst in there evaluate the bearings & bigends etc. even if they're sound you really want to find out now because if not you might waste your money/time rebuilding the top end, only to find that you have to do it all again plus repair the bottom end. I think you'll be very lucky if the only damage is the valves...
I'd be interested to know why the belt gave way, was it beyond the service life or tight, loose or bearing failure. Steve
Your so right off to see the gentleman who is going to do the work on tues wed and see where we go from here and exactly what's going on in there all I know at the moment is it turns over so the bottom end seems ok and it needs 2 new valves Don t why it broke there was a ticking sound comming from engine then a small rumble and that was it The stuff that looks like grass is what's left of the vertical belt
This is the piston that kissed the valves , next the head is getting checked I was only going about 25-30mph
But it's the piston speed that matters, not the road speed. That said, the piston looks OK but I'd still be wanting a good investigation at the bottom end. My Guzzi had a piston to exhaust valve interface last year, bent both exhaust valves and pistons were just dinged. I took the rods out to check for straightness and changed the big end shells anyway as a precaution (even though they looked fine) as they were cheap enough, but you can do all that through the sump and without splitting any cases on a Guzzi. Good luck...
Looks to me that the belt tensioner was tightened the wrong way so the belt rubbed on itself. Who fitted them?
luckily I was in Sunday traffic entering a town Pickering so I d say 3-4 rpm range so yes very lucky , would the slipper clutch help in this situation ? Belts fitted by a worker of a mate whom was sacked a while ago not a shop, my mate been a great help though Fitting new pistons and checking everything else as we go
