How hot?

In the air-cooled VW world, we say the engine temperature is too hot if you can't grab the oil dipstick for any length of time.

I realize it's unscientific, but how hot is too hot for our engines? Where is a good place to check? I touch the jugs near the sparkplugs, and I judge that if I can remain in contact with the engine for a few seconds without burning my hand, then the engine isn't overheating.

Is this a fair assesment? Got a better idea?

Thanks.

 

You would think that after 25+ years these bikes would all be in the grave yard from overheating if that was an issue. Really the only thing that suffers from high engine temperatures is the oil which begins to break down quicker as the temperatures increase. Use higher viscosity oils during the warmest part of the year (20W-50) and keep up with your oil changes and your bike will be fine.

 

Well I'm asking this question because my bike was podd'ed and 4-1 by the PO. I'm running a set of stock carbs that I scored from ebay a while ago. I finally got it idling well, so that I can cut off the fuel enrichment circuit completely and ride it normally. I think it runs pretty darn well.

Now that I'm doing that, my plugs are whiter. Not brilliant white, but whiter. I don't want to burn a hole in the piston crown.

 

Sushi, I don't believe you are going to hole a piston cause the engine is hot, its because of preignition at the spark plug due to running to lean. With stock carbs & pods & 4-1 it will run lean, that is why your plugs are whiter. Are they white like new or do they have some color? I'll post a couple of pics if I have them to show good (tan color) & bad
(to lean,white). Well I didn't have a photo of lean but IMHO if yours are whiter that the photo you need to back your mixture screws out somemore.

Guys if I am wrong on this please post. Thanks
Gregg

 

They aren't that tan but they aren't white like new either. Hm..

 

I would tweek them a degree richer. It wouldn't hurt if you posted pics of where all 4 are at now before you tweek rich & after you tweek. That way everyone will know where you are at.

 

If there is no color on the Ceramic surrounding the Spark Plugs Center Electrode, the Mixture is too Lean.
A Critically Lean Mixture will damage the Engine.
If the Mixture is so lean that the Combustion Stroke has such an extraordinarily Hot Burn the Piston Crowns are at risk for being welded through.
Friction is increased because the Power Stroke burns-off the Oil sheen on the Cylinder; leading to the Piston Skirt being damaged for insufficient lube.
Burned Valves or Valve Seats become problematic ... as do Valve Stem Seals getting dried-out from being over-heated.

If increasing the Supplemental Richness form Pilot Mixture Screws don't do the trick ... you need to Increase the Pilot Fuel Jet's size to allow more Fuel to be Metered in.

 

Thanks Rick (and the rest). I'll pull the plugs again and check. Is it possible to change to a lower temperature plug as well?

 

Rick correct me if I'm wrong but a colder plug will not help a lean condition. You are gonna have to adjust those mixture screws & hope that works or rejet.

 

Gregg, you are correct. The colder plug will not fix a lean condition.
Sushi, tweak them a tad richer eh?

 

Ok, will do. And it seems that what you're saying is that engine temperature is not necessarily a good indicator of a critically lean condition?

Meaning, even if my engine doesn't seem red-hot, that I could still be critically lean and damaging things?

 

Well, I re-inspected my plugs after dialing out. I'm glad to say that I'm not critically lean. I'm not perfectly equal between cylinders but they are all varying degrees of tan or even just a touch sooty. None are white now. I actually may not have to re-jet. That might be a positive by-product of the number of baffle plates on my SuperTrapp.

I'll keep fine-tuning until they are all equal. I couldn't be more pleased with the bike's performance. Solid idle, hard pulling, reasonable gas mileage, easy starting hot or cold, F/E circuit works perfectly.

Sometimes I look back at it as I walk away from the parking spot. :wink:

 

Congrats Sushi, glad to hear you have the problem coming your way. Just keep tweeking those screws (a degree at a time) until you get that tan color about the same on all 4 & you will be money. A sweet running bike is a thing of beauty isn't it? Especially when you did it yourself.
Ride safe & enjoy,
Gregg