BMW Luxury Touring Community banner

1 - 15 of 15 Posts

·
Registered
Joined
·
399 Posts
Discussion Starter #1
Hi All,

Today for the first time I checked my valve clearances with spark plugs removed. My bike only has 17,000 miles so I assumed they would all be in spec and thought this would just be a base line measurement. Well they all fell within spec except for one intake valve that measured 0.005" (0.13 mm). Minimum per spec is 0.006" (0.15 mm). I triple checked it and that's it.

I am tempted to button it back up and check it again next time, unless the wizards here think that's a mistake. Opinions? Thanks, Jim
 

·
Registered
Joined
·
12,165 Posts
Hi All,

Today for the first time I checked my valve clearances with spark plugs removed. My bike only has 17,000 miles so I assumed they would all be in spec and thought this would just be a base line measurement. Well they all fell within spec except for one intake valve that measured 0.005" (0.13 mm). Minimum per spec is 0.006" (0.15 mm). I triple checked it and that's it.

I am tempted to button it back up and check it again next time, unless the wizards here think that's a mistake. Opinions? Thanks, Jim
I will run a loose valve, but not a tight one. Running a loose valve may generate a little valve noise, but nothing else. A tight valve can start valve burning, which will accelerate over time. The issue is that cam grinds incorporate "clearance ramps", which take up the clearance slowly (in relative terms) to reduce shock and noise before the real opening ramp takes over. If the valve clearance is tight, the valve starts to crack open on the relatively slow clearance ramp. You want the valve to open as quickly as possible right at the start because the exhaust gasses are at their highest pressure at that time, and cracking the valve open a little slower causes the very high pressure gas to stream through the small opening very fast (can be supersonic speed), and this can start tiny erosion tracks. Once these are in place, you get leakage through them all the time, and they grow.
 

·
Registered
Joined
·
399 Posts
Discussion Starter #3 (Edited)
David, Thanks for your response. I know that one valve is tight and I guess I was asking how tight is too tight. To me it seems the intake side is not as critical as exhaust.

All other valves in spec but are near the tight end or middle of range: 4 inlet valves at 0.007" (0.18 mm), 3 inlet valves at the minimum 0.006" (0.15 mm), 4 exhaust valves at the minimum 0.010" (0.25 mm) and 4 exhaust valves at 0.011" (0.28 mm).

If the buckets come in 0.05 mm increments and I have to dig in deeper to change out one, then I'll probably change out 8 buckets to bring clearances from mid to max spec clearance.

Oh well, more work lies ahead!
 

·
Registered
Joined
·
2,684 Posts
I'd re think the max. Most bikes come from the factory at about 75% of the range. And with all the ones you mention at the edge, for sure just go for it.
 

·
Premium Member
Joined
·
2,086 Posts
I would do all 8 that are at min or less.
You may be able to swap buckets around. After that,post here what you need and maybe trade with someone else.
Take all at min one bucket size thinner. The intake at .005 could go one or two sizes thinner.

DanM
 

·
Registered
Joined
·
399 Posts
Discussion Starter #6 (Edited)
With only one valve a silly little thousandth out of spec, I am / was so "on-the-fence" whether to just button it up and check it again in 5-6000 miles next year, versus not be lazy & pull all the buckets out to measure and swap out as needed to get them in a better range. As much as I want to put it back together and ride, I'll defer to the better logic here and do it right. With work travel this week it will be next weekend, but I'll post up what I find, what I can exchange and what sizes I need to obtain. Thanks to all for your input!
 

·
Registered
Joined
·
211 Posts
I would do all 8 that are at min or less.
You may be able to swap buckets around. After that,post here what you need and maybe trade with someone else.
Take all at min one bucket size thinner. The intake at .005 could go one or two sizes thinner.

DanM
Shouldn't that be thicker?
 

·
Registered
Joined
·
399 Posts
Discussion Starter #8
Shouldn't that be thicker?
No, Dan got it right. That valve clearance is 0.13 mm - if I go to the next size thinner bucket it will put the clearance at 0.18 mm right in the middle of range.
 

·
Registered
Joined
·
211 Posts
Sorry about that. I forgot that the measurement is of the gap when the valve is closed, therefore thinner bucket gives larger gap.
 

·
Registered
Joined
·
399 Posts
Discussion Starter #10
--------------------------------------------------------------------------------

Tonight I pulled the buckets out and measured them. PDF of my spreadsheet is attached. In summary:

To bring the one out-of-spec valve into range I will need one 2.90 and will have one 2.95 spare.

To bring all the valves to the mid to max clearance, I will need two 2.70 and two 2.85. I will then have two 2.80 and two 2.95 as spare.

Does anyone want to trade? Thanks, Jim
 

Attachments

·
Premium Member
Joined
·
398 Posts
Excellent spread sheet. I have an 2005 LT with just shy of 50k miles. I have one intake valve at .05 for the last two inceptions with no issues. On my 2006 LT, I did have to change out three buckets. I went to my local dealer, North County BMW in San Diego, and they thought I was from mars. I asked to trade some buckets and there inventory of buckets was very limited. I have had to take the duel cam shafts off to pull both cams. This job is not extremely difficult but should not be for the faint of heart. It is a challenging repair. My point is will your bike implode if you are are at .05 instead of .07 clearance? I'm betting not. Although I am not an engineer just an LT rider with over 75,000 miles on three lts. I may get some flake but world wide, how many riders have never, I mean never changed coolant since they have owned the bike. I ride with two long time LT riders. Both have never changed the brake fluid in the control circuit since they've owned the bike. Are they headed for immanent brake down doom? Who knows. I've never had to leave them behind for any reason.

I think we are conditioned to believe our bikes need these kinds of TLC to maintain the performance we've come love. I don't buy it. I for one run Mobile One 15/50. I easily go 12K miles between changes. Oil burn is the same when I was running 20./50 beemer oil. The difference now Is I can top off a any Walmart that sell 15/50 oil. We have a tendency to treat these bikes like Faberge eggs. They are much more robust than most people give then credit for.
 

·
Registered
Joined
·
399 Posts
Discussion Starter #12 (Edited)
Todd,

I think you are right that there is an overabundance of caution when it comes to these things and BMW service schedules in general. In another parallel thread, Voyager reported back that after many miles running too tight intake valves at 0.10 mm, it is no worse for wear. My worst valve is 0.13 mm, or only 0.02 mm under spec. It's the intake side - I doubt burning those valves is a real risk. I am also again questioning the logic of needing to run at higher clearances than minimum specified. In range is in range. I also hear that the wear rate is extremely low, so why go to the loose end?

That was the one little bird talking in one ear but the other one prevailed. I went through the exercise to also document what I have for future reference. Mine is a low mileage LT (hope to put tons of miles on it when I can quit working and get more time) and wanted to nip any possible issues in the bud to get maximum life out of this thing.

I like to tinker and now am confident I can do this work without a big deal. If I don't come up with a 2.90 bucket now, I'll button it back up and order one for next service. I don't have the luxury of a dealer nearby to pop in and buy one. I hate to see my bike torn down when I want to ride!

Thanks for your opinion and view. That's what makes this forum great.
 

·
Registered
Joined
·
399 Posts
Discussion Starter #13
Curtis was very kind and generous to send me a 2.90 bucket! :dance:

Thanks Curtis!
 

·
Registered
Joined
·
12,165 Posts
Todd,

I think you are right that there is an overabundance of caution when it comes to these things and BMW service schedules in general. In another parallel thread, Voyager reported back that after many miles running too tight intake valves at 0.10 mm, it is no worse for wear. My worst valve is 0.13 mm, or only 0.02 mm under spec. It's the intake side - I doubt burning those valves is a real risk. I am also again questioning the logic of needing to run at higher clearances than minimum specified. In range is in range. I also hear that the wear rate is extremely low, so why go to the loose end? ----------------
You are right. Intake valves are not very susceptable to burning, as they do not open when cylinder pressure is high, and the intake mixture cools them. Exhaust valves are far more critical, as they open when the pressure is high and the exhaust gasses flowing through them are very hot.

I always set mine to high end of clearance, only because they always wear tight, and this just gives you more time before they need changing.
 

·
Registered
Joined
·
12,165 Posts
Todd,

I think you are right that there is an overabundance of caution when it comes to these things and BMW service schedules in general. In another parallel thread, Voyager reported back that after many miles running too tight intake valves at 0.10 mm, it is no worse for wear. My worst valve is 0.13 mm, or only 0.02 mm under spec. It's the intake side - I doubt burning those valves is a real risk. I am also again questioning the logic of needing to run at higher clearances than minimum specified. In range is in range. I also hear that the wear rate is extremely low, so why go to the loose end? ----------------
You are right. Intake valves are not very susceptible to burning, as they do not open when cylinder pressure is high, and the intake mixture cools them. Exhaust valves are far more critical, as they open when the pressure is high and the exhaust gasses flowing through them are very hot.

I always set mine to high end of clearance, only because they always wear tight, and this just gives you more time before they need changing.
 
1 - 15 of 15 Posts
Top