Carb sync - valve adjustment indicator?

[Miles Long]

For you motor gurus -
Damon just posted something interesting in another thread - "Erratic idle when hot"
Quote - "When was the last time your valve clearance checked and/or adjusted? I have seen when a valve adjustment was needed the idle rpm & vacuum readings would be bouncing all over due to leaking intake valves once engine was @ operating temps. allow the engine to cool completely down then thing would be normal until back @ operating temps."

My question - how reliable can vacuum readings be, to determine valve adjustment status? Given that both intake and exhaust valve clearances generally decrease with accumulating mileage, and that any "tight" valve (not completely closing) will effect both compression and vacuum.......
If a successful carb sync is done with the bike fairly cold, and the vacuum readings remain consistant after the bike is well into operating temperatures, can one assume that all valves are closing completely?...still within their minimum clearance limits?
Thanks in advance for all responses
Cheers!

 

[Damon]

Miles,
While performing a carb sync with the engine @ operating temps, I will generally look for a few indicators. What is the value of the overall vacuum level once all carbs have been leveled-off @ 1000rpm, (is this value within recommended range) and/or while setting the vacuum level across all four carbs you find one that will not retain/maintain the setting & continues to requiring adjustments. This is some of the indicators that will lead me to question a valve clearance issue. This of course is with all things being good as it relates to vacuum leaks etc.

For you motor gurus -
Damon just posted something interesting in another thread - "Erratic idle when hot"
Quote - "When was the last time your valve clearance checked and/or adjusted? I have seen when a valve adjustment was needed the idle rpm & vacuum readings would be bouncing all over due to leaking intake valves once engine was @ operating temps. allow the engine to cool completely down then thing would be normal until back @ operating temps."

My question - how reliable can vacuum readings be, to determine valve adjustment status? Given that both intake and exhaust valve clearances generally decrease with accumulating mileage, and that any "tight" valve (not completely closing) will effect both compression and vacuum.......
If a successful carb sync is done with the bike fairly cold, and the vacuum readings remain consistant after the bike is well into operating temperatures, can one assume that all valves are closing completely?...still within their minimum clearance limits?
Thanks in advance for all responses
Cheers!

 

[Miles Long]

Miles,
While performing a carb sync with the engine @ operating temps, I will generally look for a few indicators. What is the value of the overall vacuum level once all carbs have been leveled-off @ 1000rpm, (is this value within recommended range) and/or while setting the vacuum level across all four carbs you find one that will not retain/maintain the setting & continues to requiring adjustments. This is some of the indicators that will lead me to question a valve clearance issue. This of course is with all things being good as it relates to vacuum leaks etc.

Thanks Damon
I've only checked the valves on my bike once, at 56k Kilometers, only one intake valve was a tad tight. All other intakes and exhausts within specs.
I met Sean Morley once personally, and mentioned this to him. He told me that given the way the bike is driven (mostly highway, revs rarely about 5k for extended periods), I should not have to check the valves again for about the same duration.
Now at 100k. The engine is still performing admirably. Starts instantly, idles @1k rpm at all operating temps, pulls well, no hesitation or flat spots.
When it comes to the engine, carburation and exhaust, my philosophy has always been "If it ain't broke, don't fix it" (anyone that has seen my bike knows that everything else has been fair game)
Unless you or others advise me differently, or the bike starts to misbehave, I'll forgo the next valve check for awhile yet. I will check the sync again to make sure readings are consistent throughout the operating temp. range.
BTW - what is the recommended overall vacuum reading?
Cheers!
p.s. and when setting valves, seeing how they generally tighten up - is it logical to set them at the maximum recommended clearance?

 

[m-cman]

I usually set them on the high end or upper half of the range.

 

[Damon]

Miles,
You must be one of the lucky ones!
If I understand the 600 mile service requirement ( 1st warranty checkup @ 600 miles from the dealership) one of the many things they are paid by Yamaha to inspect is the valve clearance checks & adjust as required. In most cases the dealer/stealer never performs this part of the checkup. What I find on most of the V-max's I service is generally somewhere within the first 13K ~ 25K miles some of the valves need to be adjusted. Once this adjustment has been completed you generally never have to go back even though the service manual stated something about every 25K~45K afterword's. The frequency I use on engines I build for my personal use is during the assembly I'll set the intakes to .006 & the exhausts to .010 with stock cams. Then somewhere around 3k ~ 4k miles I'll re-visit & adjust as needed, @ this point I'll plan on not making any further adjustments unless I suspect an issue has arrived due to vacuum level checks. I have a dual scale digital vacuum meter that has a high resolution function, this allows me to verify the vacuum level at idle speed once everything is balanced is @ or above 26 KPA's non California models. With a good valve adjustment I'll generally see 27 ~ 30 KPA's

Thanks Damon
I've only checked the valves on my bike once, at 56k Kilometers, only one intake valve was a tad tight. All other intakes and exhausts within specs.
I met Sean Morley once personally, and mentioned this to him. He told me that given the way the bike is driven (mostly highway, revs rarely about 5k for extended periods), I should not have to check the valves again for about the same duration.
Now at 100k. The engine is still performing admirably. Starts instantly, idles @1k rpm at all operating temps, pulls well, no hesitation or flat spots.
When it comes to the engine, carburation and exhaust, my philosophy has always been "If it ain't broke, don't fix it" (anyone that has seen my bike knows that everything else has been fair game)
Unless you or others advise me differently, or the bike starts to misbehave, I'll forgo the next valve check for awhile yet. I will check the sync again to make sure readings are consistent throughout the operating temp. range.
BTW - what is the recommended overall vacuum reading?
Cheers!
p.s. and when setting valves, seeing how they generally tighten up - is it logical to set them at the maximum recommended clearance?

 

[dannymax]

Miles,
You must be one of the lucky ones!
If I understand the 600 mile service requirement ( 1st warranty checkup @ 600 miles from the dealership) one of the many things they are paid by Yamaha to inspect is the valve clearance checks & adjust as required. In most cases the dealer/stealer never performs this part of the checkup. What I find on most of the V-max's I service is generally somewhere within the first 13K ~ 25K miles some of the valves need to be adjusted. Once this adjustment has been completed you generally never have to go back even though the service manual stated something about every 25K~45K afterword's. The frequency I use on engines I build for my personal use is during the assembly I'll set the intakes to .006 & the exhausts to .010 with stock cams. Then somewhere around 3k ~ 4k miles I'll re-visit & adjust as needed, @ this point I'll plan on not making any further adjustments unless I suspect an issue has arrived due to vacuum level checks. I have a dual scale digital vacuum meter that has a high resolution function, this allows me to verify the vacuum level at idle speed once everything is balanced is @ or above 26 KPA's non California models. With a good valve adjustment I'll generally see 27 ~ 30 KPA's

Damon....26 KPA's is about 20 cm/hg on the Carbtune, correct?

Do you find the Cal model carbs run lower vacuum as a rule?

 

[Damon]

Danny,
If I remember correctly 26 KPA's = 19 inches of lift / 200 mm hg's / 7.88 inches of hg's. I don't work with too many Cal bikes but the spec's call for them to run higher 33+KPA's maybe they also require a higher idle speed?

Damon....26 KPA's is about 20 cm/hg on the Carbtune, correct?

Do you find the Cal model carbs run lower vacuum as a rule?

 

[Miles Long]

Miles,
You must be one of the lucky ones!
If I understand the 600 mile service requirement ( 1st warranty checkup @ 600 miles from the dealership) one of the many things they are paid by Yamaha to inspect is the valve clearance checks & adjust as required. In most cases the dealer/stealer never performs this part of the checkup. What I find on most of the V-max's I service is generally somewhere within the first 13K ~ 25K miles some of the valves need to be adjusted. Once this adjustment has been completed you generally never have to go back even though the service manual stated something about every 25K~45K afterword's. The frequency I use on engines I build for my personal use is during the assembly I'll set the intakes to .006 & the exhausts to .010 with stock cams. Then somewhere around 3k ~ 4k miles I'll re-visit & adjust as needed, @ this point I'll plan on not making any further adjustments unless I suspect an issue has arrived due to vacuum level checks. I have a dual scale digital vacuum meter that has a high resolution function, this allows me to verify the vacuum level at idle speed once everything is balanced is @ or above 26 KPA's non California models. With a good valve adjustment I'll generally see 27 ~ 30 KPA's

Thanks, Damon
No, the dealership didn't do the valves during the bike's initial warranty check, and as a few years ago, they didn't employ anyone that was familiar with the max enough to do a valve adjust. They freely admitted this. Luckily, I have a friend in Halifax that knows the Max(and Ventures) inside out, so it's only a short hop for me to go for his help and knowledge.
As for the vacuum being drawn, I found a pic of the last time I checked.
-10 in./hg. @ 1500 rpm Converts to -25.5 cm./hg.
Cheers!

 

[dannymax]

Danny,
If I remember correctly 26 KPA's = 19 inches of lift / 200 mm hg's / 7.88 inches of hg's. I don't work with too many Cal bikes but the spec's call for them to run higher 33+KPA's maybe they also require a higher idle speed?

Thanks Damon....I see Cal. carbs come thru now and again but, of course, they test like the others cause I use the same test bike for every set of carbs.

 

[sdt354]

Damon....26 KPA's is about 20 cm/hg on the Carbtune, correct?

Do you find the Cal model carbs run lower vacuum as a rule?

Read my mind Brother. I'm getting 21 hg. Just checked last night out of paranoia. Actually, my sync was a little off. My bike will run funky at idle after it's very well warmed up. Just did the valves this past spring. set at .006/.010. Did need adjusting after 25k, nothing drastic though.

 

[dannymax]

I will say that, in my limited experience with VMax and MaximX 5-valve motors, the VMax appears to be much more forgiving related to mileage and shim wear. No doubt due to the shim design itself....the VMax is a large beefy wafer that sits on top of the bucket with the cam lobe making direct contact. The MaximX has the shims on top of the valve stems, under the buckets which the cam lobes make contact with....the shims are also tiny little buggers (about the size of the eraser on a pencil) and are very difficult to hang on to. (The shims are in the white board with all the holes, 1st pic)

The valve lash check interval for the X (after the initial check) is 26,600 mi (42K Kliks)....I checked mine at 14K miles and all 20 needed changing.....and it's a process!

My '96 Max I did at 38K miles (strongly suspect they were never done....and this bike had obviously seen many hot suppers!) and they needed no shim replacement at all.