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Falco |
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
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Falco Traffic Copper
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Kickstart |
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Kickstart The Oracle
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Pete. |
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Pete. Super Spammer
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Posted: 00:10 - 17 Apr 2017 Post subject: |
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Never heard of valve stems stretching. Clearances close because the valve sinks into the seat. ____________________ a.k.a 'Geri'
132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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Falco |
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Falco Traffic Copper
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jaffa90 |
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jaffa90 World Chat Champion
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Pete. |
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Pete. Super Spammer
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Posted: 08:32 - 17 Apr 2017 Post subject: |
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No idea what bike it is but in general shim under bucket valves usually do impressive mileages without adjustment. At 23k miles I would have expected no more than one minor adjustment and only a size or two at that. If he's getting down to minimum shim size at that mileage I would say it's going to get very expensive sometime soon. ____________________ a.k.a 'Geri'
132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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Kickstart |
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Kickstart The Oracle
Joined: 04 Feb 2002 Karma :
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Posted: 09:48 - 17 Apr 2017 Post subject: |
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Hi
Not sure on the bike. On some (eg, Yamaha FZ750) at 23K they are not even due to have been checked for the first time (and being terminally lazy I left mine until 60k). In general they rarely need changing. But if a very old bike (from before unleaded fuel being used in the USA for example) then they might not have hardened valve seats.
Shim safe thickness will depend on on the design. Personally I am dubious about grinding them down (for a start it is going to be bloody annoying the next time you do the valves, and choose the shim sizes based on what is written on the current shims). If you do then it needs to be done very carefully and accurately. Some are under bucket, some on top of the bucket. Some bike spit them shims out occasionally at the best of times.
Changing valve seats is a fairly specialised job. I would expect most mechanics would remove the head and send it away, or if a fairly common engine just tell you to source a 2nd hand engine as being a cheaper and quicker solution.
All the best
Katy ____________________ Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
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Falco |
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Falco Traffic Copper
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Posted: 12:28 - 17 Apr 2017 Post subject: |
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jaffa90 wrote: | """"""""""""1) Is this kind of wear normal for 23K? I can't imagine the engine lasting to 100K if it keeps chewing up valves/seats at this rate."""""""""""""""""""""""""""
Have you a picture of the spark plugs and the mileage they have done?
Also have you heard the cooling fan kick in and when?
When was the last coolant change done? |
No sorry, I put new spark plugs in about 700 miles or so ago, I doubt they will show anything. The old ones came with the bike and I have no idea what their millage was, they looked fine, perhaps a touch lean but it was marginal.
I have not heard the cooling fan at all, but the temperature gauge is always at the bottom by the time I stop at each end (there are longish runs to allow it to cool). The gauge does work and goes up and down as I'd expect on warm days and in heavy traffic.
Last Coolant change was about 500 miles ago, no idea before then (I did around 500-600 on the old coolant, but the temp gauge has never gone above the 1/3rd mark)
Pete. wrote: | No idea what bike it is but in general shim under bucket valves usually do impressive mileages without adjustment. At 23k miles I would have expected no more than one minor adjustment and only a size or two at that. If he's getting down to minimum shim size at that mileage I would say it's going to get very expensive sometime soon. |
It's a CB500S (2001). It's very odd, the shims in there were all fairly big (210 down to 192) but considering the odd sizes I assume it has been done at some point, so I am uncertain why the clearances have closed so much in such a short time/millage.
Kickstart wrote: |
Hi
Not sure on the bike. On some (eg, Yamaha FZ750) at 23K they are not even due to have been checked for the first time (and being terminally lazy I left mine until 60k). In general they rarely need changing. But if a very old bike (from before unleaded fuel being used in the USA for example) then they might not have hardened valve seats.
Shim safe thickness will depend on on the design. Personally I am dubious about grinding them down (for a start it is going to be bloody annoying the next time you do the valves, and choose the shim sizes based on what is written on the current shims). If you do then it needs to be done very carefully and accurately. Some are under bucket, some on top of the bucket. Some bike spit them shims out occasionally at the best of times.
Changing valve seats is a fairly specialised job. I would expect most mechanics would remove the head and send it away, or if a fairly common engine just tell you to source a 2nd hand engine as being a cheaper and quicker solution.
All the best
Katy |
Bike is from 2001, so it's not that. Definitely seems like something is wrong with this amount of wear. After some consideration I went for a shim set, to cover me for future adjustments as well, without the hassle.
If changing the engine is the cheaper solution, that sounds like a pretty expensive (£180+ on ebay for the really scabrous ones and that doesn't even cover labour costs to get the old one out and the new one in).
I don't seem to have much luck getting bikes with healthy engines. ____________________ I tell you what, mathematically, I'm having it |
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Tdibs |
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Tdibs Traffic Copper
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Falco |
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Falco Traffic Copper
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yen_powell |
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yen_powell World Chat Champion
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Falco |
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Falco Traffic Copper
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Robby |
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Robby Dirty Old Man
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Falco |
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Falco Traffic Copper
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Posted: 21:15 - 17 Apr 2017 Post subject: |
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Robby wrote: | Either the engine is terminal - in which case I wouldn't waste the money on shims and would just ride it til it dies and then change the engine - or you cocked up the measurement.
The majority of the problems inside the engine that I see are down to someone misdiagnosing a problem or cocking up a routine bit of maintenance and deciding to strip the engine.
This gives memorable things like "It's misfiring, must be rings, I'm going to change the rings" (spark plug was loose), or "It's burning oil, must be the valve stem seals, I'm going to rebuild the head" (oil filter was loose). |
Honestly, I'd be happy to say that its human error on this one, but as far as I can tell, I have done the checking correctly.
Only thing I can think of is that I have seen a couple of how-to-s that show the cam lobes as pointing away from each other horizontally, rather than at an angle. The problem is, if I do that, the the marks on the sprockets won't be level with the engine casing (which is specifically mentioned in the haynes).
I suppose I could put it back together tomorrow with the old shims and try adjusting and checking again... ____________________ I tell you what, mathematically, I'm having it |
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Kickstart |
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Kickstart The Oracle
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jaffa90 |
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jaffa90 World Chat Champion
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Posted: 00:32 - 18 Apr 2017 Post subject: |
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trevor saxe-coburg-gotha |
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trevor saxe-coburg-gotha World Chat Champion
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Falco |
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Falco Traffic Copper
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A100man |
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A100man World Chat Champion
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Posted: 14:49 - 18 Apr 2017 Post subject: Re: Valves Wearing? |
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Falco wrote: | Just calculated new shim sizes to adjust clearances, every valve was very tight and a couple of the new shims will be as low as 130.
There won't be much adjustment left when these are replaced, is this a sign the valves themselves are wearing? |
Hang on, if they are that bad (tight) you wouldn't be able to get a feeler in there at all. Not mixing metric and imperial measurements by any chance are you? What measurements are you actually getting with the old shims? ____________________ Now: A100, GT250A, XJ598, FZ750
Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600 |
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Falco Traffic Copper
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iansoady |
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iansoady Borekit Bruiser
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Falco |
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Falco Traffic Copper
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Fizzer Thou |
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Fizzer Thou World Chat Champion
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Posted: 21:53 - 18 Apr 2017 Post subject: |
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It may well be that the valves are like this and worn unevenly (new valve on the right)
https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/CIMG2957.jpg
The new valves were lapped in and gave a perfect seal.Sometimes the seats need to be recut,but in this instance it was not necessary ____________________ Just talk bikes.What else is there?
Always have a 'Plan B' |
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Old Thread Alert!
The last post was made 6 years, 346 days ago. Instead of replying here, would creating a new thread be more useful? |
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