Spark Plug

[wxp]

Anyone know anything about specific heat ranges for plugs in the r65...When should a colder plug be used as opposed to a hotter plug, Does the hot plug burn more oil, create a "hotter" combustion cause the engine to run "hotter" ??

Some input on the above would be great.  

Also, RE: the carbs; when tuning/adjusting, the screw on the bottom, is that the idle adjustment screw or an air mixture screw. if the air mixture screw does turning it in cause a leaner burn & out a richer burn??

Thanks for the help


Bill

[Rob Valdez 79 R65]

I don't really know the anwers to your spark plug answers, but they might be in here:

http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml


The screw on the bottom of the carb is an air mixture screw.

The idle adjustment is done with the screw that pushes down slightly on the throttle control, next to the throttle cable.

If I were you, I would get one of the BMW rider's handbooks for your model.  It is filled with pictures and explainations of everything you need to get started tuning.

[MrRiden]

About the carbs:
It is a true "mixture" screw. It actually regulates a metered fuel air mix as opposed to being an "air" or "fuel" screw. This came up not to long ago and an excellent diagram was posted to prove I'm not being a smart guy.
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1267758438

As for heat range. It refers to the amount of heat a plug will retain or dissipate to the cylinder head as I understand it.

[wxp]

I don't really know the anwers to your spark plug answers, but they might be in here:

http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml


The screw on the bottom of the carb is an air mixture screw.



The idle adjustment is done with the screw that pushes down slightly on the throttle control, next to the throttle cable.

If I were you, I would get one of the BMW rider's handbooks for your model.  It is filled with pictures and explainations of everything you need to get started tuning.

Thats what I thought about everything. I have a clymers manual but I didn't seem to make much sense to me. Had a friend show me a few things this wkend I now under stand the procedures involved its just a matter of tweeking them now.. I think I hve it too rich right now, I smell fuel. its not leaking anything.  

I took the carbs off this winter to rebuild them & after finally doing so I put them back on & got it running this weekend, I am at the tweek stage & needed to learn about the function of the screws & make sure of what i'm doing.

It runs good & strong, has a strange whir sound to it, during the initial twist of the throttle, it wants to stall, like taking a gulp of air then trying to chase it w/some fuel, if I'm careful I can keep it from stalling but not all the time.

I read another article here, sounds a lot like what I'm experiencing, I'll read it again to be sure.

[wxp]

the ngk article posted above is a good article to better understand spark plugs

[Barry]

Plugs work best ie spark more easily when they are operating in the correct temperature range.

The recommended plug is usually fine however if you are experiencing fouling or oiling up of the standard plug it's worth bearing in mind that the recommended spark plug heat range will have been conservatively set by BMW meaning it will be cold enough to be safe at sustained maximum speed. If you never ride at sustained maximum speed then it's probably safe to use a one grade hotter plug.

I have safely used a 1 grade hotter plug on my bike and currently use a 1 grade hotter plug on my 21 year Merc 190E because it offsets the fact that it's starting to burn a little oil at 110,000 miles and in any case I rarely use more than half it's performance.  

Using a colder than standard plug makes no sense at all as it will never get hot enough unless on a modified/racing engine.

[Rob Valdez 79 R65]

Good summary, Barry.  I will copy it to the FAQ post I made of the NGK article.

[bubby-joe]

Heat range of any plug has to do with heat transfer.  A cold plug would have a shorter insulator and be deeper into the plug and be cooler running longer to warm up, a hotter plug would have more insulator exposed to the burning gasses in the cylinder chamber and burn hotter to burn off any deposits.  

A colder plug may glaze and not burn off oil deposits and eventually fail.  A hotter heat range may prevent this to some extent.  

The plugs heat range should have no effect on oil consumption, that's the job of the piston rings and valve guides and seals.

So if your oil  fowling plugs (black crusty deposits)(bridging the gap) try a hotter range then look to the rings and valve guides to find the oil consumption problem, if your cooking the plugs (bone white and blistered) try a cooler heat. range.

With my 80 R-65 I can't get the recommended heat range so it's better 1 range hotter than colder, this is the first engine in years to give me a text book plug (perfect burn pattern and color) after a 10 mile ride.

[Lucky_Lou]

it's worth bearing in mind that the recommended spark plug heat range will have been conservatively set by BMW meaning it will be cold enough to be safe at sustained maximum speed.

Any one know what the Safe Sustained Maximum speed is on a r65 ??
Lou

[Rob Valdez 79 R65]

Any one know what the Safe Sustained Maximum speed is on a r65 ??

Without saddlebags on, WFO, I'd say - engine-wise speaking, of course.

I don't know if a R65 will redline in 4th or 5th.  
Whenever I'm not afraid of dying, I'm afraid of cops.  
Whenever I'm not afraid of cops, I'm afraid of dying.

[Barry]

Any one know what the Safe Sustained Maximum speed is on a r65 ??

It will be whatever the continuous permitted revs are. I think 7250 rpm but I'm sure it's in the manual. For all practical purpose it will be as fast as you can go in 5th and maybe even 4th most of the time. Who goes that fast anyway - not me.

[Ed Miller]

I've gotten mine up just over 7000 rpms in top gear, once.  I've read that the redline on BMWs is the "Safe Sustained Maximum speed".  

Of course, I was only going 85 mph.  

[Barry]

From the riders handbook and assuming R65 final drive of 3.44:1

Max permissible engine speed (red line) is 7650 RPM = 114 mph

Max continuous engine speed 7300rpm = 109 mph

I think a down hill straight and a good following wind would be needed to get upto either of these speeds bearing in mind they are real MPH not what the speedo reads. Speeds for an R45 are approx 10% slower.