Valve Lash Increase

[JBurns]

I was reading through the "Oilhead Maintenance" pdf from the internet BMW riders and Oilhead riders and came across a section on increasing the valve lash which stated

 

"Valve Lash Increase - Rob Lentini

If you are like me, try this. I like low and mid-range driveability and throttle response. My R1100RS would not idle for several minutes on cold mornings until I increased valve lash. Increasing valve lash FIXED the problem, and I've

lost no discernible top-end power. Increased valve lash is equivalent to closing

the valves sooner--"milding" the cam timing.

Set the valves COLD from/to:

 

Intake: Spec: .006" to: .012"

Exhaust: Spec: .012" to: .014"

 

Your idle will be MUCH smoother and throttle response immediate but

controllable. Increase in valve noise is minimal. Valves will run cooler."

 

Now I have an 1150RS and I am doing the valve adjustment this week and was wondering about these settings. It seems like a big jump on the intake side to go from 15mm to 30mm but my bike has always idled like crap until it completely warmed up and even then it has always been a little rough. Any thoughts?

[4wheeldog]

Spark plug choice will have more effect on cold running than valve lash changes. Try the autolites. Or you can try my favorites, Denso IK22. My RT idles smoothly, albeit very slowly, without the fast idle lever, anytime the ambient temps are more than 50 degrees. Good luck.

[David R]

I went a different route. A little more fuel at idle works for me. I first set the TPS to max of the spec. Then I bought a techlusion and never looked back.

 

My bike has no O2 sensor, I deleted it. I also deleted the cat.

 

To each his own.

 

The extra fuel is only a small amount. It helps cold and hot.

 

Adjusting the valves to fix a cold start problem seems counter productive because the valve lash is different when hot too.

 

Perhaps one of those things that fools the intake air temp sensor would be a better way to get a good idle. Booster plug is what I think its called.

 

David

[JBurns]

Well I am going to change out the plugs as well during the valve adjustment but had planned to go back with NKG. May just have to do a little experimenting!

[dirtrider]

Afternoon JBurns

 

Sure go ahead & adjust the valve lash to--

 

Intake form : .006" to: .012"

Exhaust from: .012" to: .014".

 

Be a good test case & will let us know how long YOUR BMW boxer can go before having valve train issues or valve seat recession due to harsher valve opening & closing events.

 

If you don't mind accelerated valve train wear, possible valve seat issues, & more noise, then go for it.

If you run at high RPM's I would imagine you will get some valve closing bounce on those intakes set at double spec as that is WAY off the gentle cam lobe closing ramp.

 

Just keep in mind that Lentini had a valve failure on the same bike he did that valve lash testing on. No way to know if that was the cause or not. We need more test cases here to duplicate his valve damage finding.

 

My personal take on running the valve lash that far out of spec is: (IF) you can tell the difference & want to change cam timing then do it right & change the cam timing with sprocket key offset or different cams.

 

To me, changing the valve lash to change cam timing is like lowering your tire pressures by 15 PSI to get your speedometer to read correctly. Sure it can work but are the added problems brought on worth it?

 

[JBurns]

Now dirtrider that is exactly the kind of response I think I was looking for! I haven't been in the BMW world long enough to know that Lentini had valve failures on his text bike, but it's a good thing to know.

 

Your point is well taken on changing cam timing the correct way! I'm no hot rod, and I really don't want to use my RS as a test case so you have inclined me to adjust per the specs!

 

I thought everything you read on the internet was true?

[4wheeldog]

To me, changing the valve lash to change cam timing is like lowering your tire pressures by 15 PSI to get your speedometer to read correctly. Sure it can work but are the added problems brought on worth it?

 

Very well put. Smokey Yunick used to get exasperated, and say, "Everybody wants to fly without wings today!" These discussions always bring that concept to my mind.

[Peter Parts]

In the 20,000 miles or so (not really sure) I've been using a few extra thou, couldn't complain.

 

The R1100S might be a bit sharper tuned than other models and so the softening might be a bit more helpful, along with other changes I've made to move torque band lower. A little extra lash lets your hot valves cool a bit longer when seated and makes breathing a bit less radical. Not a lot, but nice... as Lentini said.

 

As somewhat goofy old air-cooled push-rod engine, the lash is a cooked number taking into account a lot of loose pieces, unpredictable temperature moves, and lot of loose mechanics.

 

By the way, it has been a few years since I last had to tweak my valves. It is baloney about eating valves?

 

Funny thing, not one of the previous posts starts with a modest, "... although I never tried it or knew anybody who did...." Pity.

 

 

Ben

[dirtrider]

Evening Ben

 

So you have been running your valves at Intake =.012"

& Exhaust = .014" for 20,000 miles now?

 

[Peter Parts]

Evening Ben

 

So you have been running your valves at Intake =.012"

& Exhaust = .014" for 20,000 miles now?

No, Just two spare thou on intake and exhaust, give or take the usual error of measurement of such things. Not much and no big consequences, as you wisely pointed out on that other thread.

 

Long time since I read Lentini (an admirable experimenter). Exactly what did he suggest?

 

Folks on this website are forever fretting about precision, compulsive maintenance, etc. Yes, sometimes (OK, rarely) it is appropriate.

 

But valve lash is a different matter on pushrod engines. The various parts expand and contract differently on different days and rides. So the engineers cook up a number that handles various factors and build-in a fudge/safety factor.

 

I build-in a bigger fudge factor. That's all.

 

Factory-knows-best adherents, take note.

 

Ben

that's my loosey-goosey approach to lash but I am ABSOLUTELY COMPULSIVE about balancing/matching the two cylinders!!!! And all boxer riders should be too.

[dirtrider]

Evening Ben

 

So we can take from all your words above that you haven't been running your valves at- Intake =.012" & Exhaust = .014" for 20,000 miles now?

 

Therefore your 20,000 miles is of no actual use to the original poster here asking if he can run the Lentini suggested .012 intake & .014" exhaust.

 

[Peter Parts]

Evening Ben

 

So we can take from all your words above that you haven't been running your valves at- Intake =.012" & Exhaust = .014" for 20,000 miles now?

 

Therefore your 20,000 miles is of no actual use to the original poster here asking if he can run the Lentini suggested .012 intake & .014" exhaust.

 

I never realized that you were a great master of medieval syllogistic logic.

 

But speaking for inductive logic, I'd say my comments were not entirely out of place.

 

What do you think?

 

Ben

[Galactic Greyhound]

I would say that inductive logic generally contains a spark of truth

[Jim Moore]

Just keep in mind that Lentini had a valve failure on the same bike he did that valve lash testing on. No way to know if that was the cause or not. We need more test cases here to duplicate his valve damage finding.

 

Actually I think he broke a piston. At the time he opined that it may have ben due to the advanced timing, his use of 87 octane gas, or simply age. The bike had 100K miles on it when it broke.

[dirtrider]

Morning Jim

 

Yes, he had piston problems but also from his findings --

 

 

Quote:-- "Cylinder head is cracked between the two intake valves.

Evidence of severe collisions within the chamber. Three out

of the four valves clearly bent and the fourth likely bent."

 

[Peter Parts]

Morning Jim

 

Yes, he had piston problems but also from his findings --

 

 

Quote:-- "Cylinder head is cracked between the two intake valves.

Evidence of severe collisions within the chamber. Three out

of the four valves clearly bent and the fourth likely bent."

 

I knew it! Maybe he set his valve lash to zero to avoid that horrible clicking noise and see what happened. Now, that's a lesson for us.

 

(Thanks Ced. and Jim.)

 

Ben

[David R]

Just for free information.

 

I read here some one asking about hot and cold valve adjustment.

 

I set mine cold by the book. I can tell when they are right.

 

This week I wanted to look at my cam chain guide so I pulled the valve cover off when the bike was HOT. Guide was fine, chain was tight, etc. While I had it opened up and HOT, I measured the valve clearance.

 

Intake .008"

Exhaust .012"

 

From this little test, things do not change much from cold to hot.

 

There is no "Magic Screw" that will make our bikes go faster. No secret little trick that only mechanics know or anything else. Set and adjust everything where its supposed to be and enjoy a smooth fine long running machine. Give it clean air, clean oil and the right fuel.

 

Ride the somebitch!

 

David

[Peter Parts]

snip

 

There is no "Magic Screw" that will make our bikes go faster. No secret little trick that only mechanics know or anything else. Set and adjust everything where its supposed to be and enjoy a smooth fine long running machine. Give it clean air, clean oil and the right fuel.

David

 

Thanks for hot data. Interesting. Truth is, your bike was already quite discrepant from operating temperature and already differently for intake and exhaust and differently if a valve or two was seated (unless you measured within one second of stopping). That's why a good fudge factor has to be built in.

 

Beg to differ, but there are lots of things, large and small that improve performance, whether "magic screw" is the right name or not. Been doing so for 46 years.

 

These range from just removing your saddlebags to grinding the rough edges inside your exhaust system to changing the ECU chip. Or improving your suspension. Or softening your valve lash. Some stuff on my writing website URL below.

 

With an ECU bike, much harder.

 

Best "magic bullet" is to lose a few pounds around your middle. Reduces weight and improves aerodynamics, eh.

 

Ben

[Stan Walker]

Best "magic bullet" is to lose a few pounds around your middle. Reduces weight and improves aerodynamics, eh.

 

Most useful thing you have ever said.

 

Stan