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Post by nickjaxe on May 11, 2022 0:01:02 GMT 1
Hi....never had anything to do with shims to set the correct valve clearance.....recently bought a motorcycle that uses shims.....PITA compared to the old screw and lock nut.
My question....I presume there is an advantage in using shims.....what is it can anybody tell me.
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Post by sorted on May 11, 2022 6:46:17 GMT 1
It’s around efficiency- using buckets with shims enables the camshaft to pretty much drive the valves directly which reduces the number of moving parts and so the space needed and weight too.
I remember my first car was a 1973 Vauxhall Viva but fitted with the 1800 slant 4 engine more common to the Magnums. That had a camshaft driving the valves directly but had a very innovative adjustment method- instead of shims, a hardened angled Allen screw through the side of the bucket was what actually sat on the valve stem. You could access this screw via a cutout in the casting with the bucket turned to the right point and - hey presto- instant valve adjustment without shims.
These days of course hydraulic bucket adjustment is the norm which is the best of both worlds.
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Post by OldGit on May 11, 2022 7:22:29 GMT 1
It’s around efficiency- using buckets with shims enables the camshaft to pretty much drive the valves directly which reduces the number of moving parts and so the space needed and weight too. ... These days of course hydraulic bucket adjustment is the norm which is the best of both worlds. It also reduces the number of components that will be subject to wear and removes the need for regular adjustment - although re-shimming is required, it's nowhere near as frequent as tappet adjustment. With hydraulic bucket tappets, some manufacturers have taken a step backwards and have a rocker arm with a roller bearing running on the camshaft to reduce wear, of course, the roller bearings are an additional wear point...
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Post by Rhubarb on May 11, 2022 9:58:33 GMT 1
What bike is it?  |
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Post by upkeep on May 12, 2022 9:17:38 GMT 1
Less valve train weight
Less maintenance
Less wear
Higher revs
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Post by trickydicky on May 12, 2022 11:26:24 GMT 1
I have a tool somewhere for doing them on the Izuzu/Vauxhall Diesel engines of the 90s. It's basically a lever/hook that goes under the camshaft and pushes the bucket/ down on the edges so you can pull the shim out with a pick/magnet and pop another one in without removing the belt and camshaft.
They always used to close up due to valve seat wear until they lost some compression and became hard to start!
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Post by rhyds on May 12, 2022 13:26:35 GMT 1
I'm guessing improved oils and harder wearing materials have made shims more popular in the last 10-15 years. My Duratec-HE/Mazda MZR 1.8 Petrol unit has shims (I think) and still sounds good at 90k miles. Older shimmed designs like Austin Rover's S series unit (the 1.6 in the Maestro/Montego) often sounded like the top end was full of bolts and sadness after less than half that.
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Post by OldGit on May 12, 2022 18:46:57 GMT 1
I have a tool somewhere for doing them on the Izuzu/Vauxhall Diesel engines of the 90s. It's basically a lever/hook that goes under the camshaft and pushes the bucket/ down on the edges so you can pull the shim out with a pick/magnet and pop another one in without removing the belt and camshaft. They always used to close up due to valve seat wear until they lost some compression and became hard to start! Ooh! I remember them! I also remember having an AstraMax with that engine (courtesy of the RAC) and getting valve bounce after 'enthusiastically' accelerating downhill on a quiet section of the M42 at night to see if it'd reach three figures on the speedo, drove it to the next job very carefully after parking up for a bit and listening for any change in the cranking speed...
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Post by nickjaxe on May 12, 2022 23:31:07 GMT 1
What bike is it?  2019 Triumph T100 Bonneville water-cooled.....all exh valves are at max gap inlets still fine....covered 2500mls....valve check not req till 10.000mls. Checked as I am looking for whats causing a tapping sound that shows its head around 30secs after a cold start.....after around 2 mis of idling it slowly disappears just like it started. Its under warranty....but the dealers dont have a clue what it is....say to me live with it. Dont trust them to work on it. |
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Post by Rhubarb on May 13, 2022 7:22:07 GMT 1
What bike is it? 2019 Triumph T100 Bonneville water-cooled.....all exh valves are at max gap inlets still fine....covered 2500mls....valve check not req till 10.000mls. Checked as I am looking for whats causing a tapping sound that shows its head around 30secs after a cold start.....after around 2 mis of idling it slowly disappears just like it started. Its under warranty....but the dealers dont have a clue what it is....say to me live with it. Dont trust them to work on it. Yes of course, I remember this now  Have you tried using a stethoscope/screwdriver to locate the noise? I assume if you fire it up and ride straight off then no noises occur 30 secs later? I'm old fashioned and tend to do just that. |
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Post by nickjaxe on May 13, 2022 7:45:49 GMT 1
No I let it idle while I put my jacket on ect.
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Post by upkeep on May 13, 2022 8:11:32 GMT 1
My Kawasaki Z900 has a small tick at idle and they all seem to do it, I had a Kawasaki ZXR750 that made a dreadful noise on start up but it was the oil running through the filter when cold and after 30 seconds the noise disappeared never worried about it.
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Post by rhyds on May 13, 2022 9:25:22 GMT 1
What bike is it? 2019 Triumph T100 Bonneville water-cooled.....all exh valves are at max gap inlets still fine....covered 2500mls....valve check not req till 10.000mls. Checked as I am looking for whats causing a tapping sound that shows its head around 30secs after a cold start.....after around 2 mis of idling it slowly disappears just like it started. Its under warranty....but the dealers dont have a clue what it is....say to me live with it. Dont trust them to work on it. Ah yes, now I remember. If you've still got issues with that bike, take the shims out and post them to the dealer (2nd class) and get them measured, saves the risk of them working on your bike!  |
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Post by nickjaxe on May 13, 2022 9:29:56 GMT 1
Got new bigger ones on the way....I have all the measuring equip.
Saying that....long time since I last used it.....needed to remind myself....more at home with imperial measurement's than metric.
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Post by upkeep on May 13, 2022 14:48:31 GMT 1
Are they above or below the bucket below I presume so cams out. I personally would not bother.
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