How long to overheat

[Cabreco]

Question,
On an 85 degree day with the engine idling at 3500 rpm standing still, how long should a DOHC go before overheating & stalling?

[Peterwh]

If you don't mind me asking, why would you want to know?  I wouldn't try it though if I were you

[sgtslag]

"idling at 3,500 RPM"?...  Idle should be around 1,000 RPM.  That really is not "idle".  You may need to adjust the idle speed, unless you are referring to something else.

If overheating is a concern, you can look into adding an oil cooler.  It won't make much of a difference idling, but it makes a world of difference running down the road.  Mine cooled my oil from 250 F, highway, two-up with luggage, to ~210 F, same load, but 10 F warmer weather (40-50 F cooling effect).

A less expensive/easier option, is to use synthetic oil, which won't break down until 400+ F (dino oils break down into carbon sludge above 250 F...).  Shell Rotella T6 (5W-40 synthetic; zero friction modifiers -- won't affect your wet clutch; SM rated auto's, CJ-4 for diesels...) is inexpensive, and very good quality.  Spins my car over, at (-10) F, in Minnesota January winters, like it was 90+ F, in July.  It also runs very well in my '79 Honda.  Cheers!

[Cabreco]

Well the reason I ask is, I have been trying to determine why oil has been dampening my left exhaust outlet & why the outside left pipe is cooler to the touch than the others.
I did a compression test & all read fine. That being said, I replaced the plugs with new NGKs & the cool pipe was as hot as the others (good right) but then the pipe started smoking (definitely oil). Someone had mentioned the PO may have put oil in the exhaust to prevent rust. Anyhow, I held it at between 3K & 3.5K for around 5 minutes or so watching the bluish smoke. Then I let it idle another 3 minutes at 1000 rpm. Then (as Forrest Gump would say) for no reason at all, she just stalled, and would not start up. This bike starts immediately at the hit of the starter button. I also notice some smoke (like when you burn off spilled oil of an engine pipe) from just under the shifter just before it stalled. I waited a few minutes and she started right up again. So I am thinking that she overheated & stalled.
BTW now there is no hint of smoke from the pipe or below the shifter.
Any thoughts (other than don't do that again LOL)
Thanks

[sgtslag]

Well, the PO of my '79 told me how he had put a small amount of oil in the exhaust pipes, right at the top, where they connect to the engine.  He said it coated the inside of the pipes to prevent rust...  I now (four years later) have one muffler rusting out, from the inside.  Does it work?  Maybe, but not well enough for me to justify pulling the pipes, adding oil, then installing new copper gaskets.  

With regards to running the engine like you did, it likely overheated -- not really a good thing.  How much, or if, it damaged it, I could not say.  Your best option is to change the oil and filter immediately, to remove all gunk from your engine.  Before you change it, though, I would recommend adding some SeaFoam to the crankcase (1 oz. per quart of oil -- 3.5 oz.), letting it idle (at 1,000 RPM) until the oil is warmed up (180 F), to suspend any crud (maybe five minutes, but no longer).  The SeaFoam will help dissolve any varnish/carbon deposits within the engine/transmission, which will either be suspended in the warm oil, or captured by the filter.  SeaFoam is available at any automotive department, or store, for around $9 per 16 oz. can.  I have used SeaFoam in my '79, twice, with 10,000+ miles since, without issue; I've also used it in my other two bikes, and three 4-wheeled vehicles' engines, without issue, over 20,000 miles on one car since treatment.  It is safe for your engine, and your bike's transmission.  Always read and follow directions.

Put in a new filter, and fresh oil of your choice.  Shell Rotella T (15W-40, high quality, friction modifier free, diesel oil:  SM rated for cars) is around $14-$15/gallon, and T6 Synthetic oil (full synthetic version; 5W-40; SM rated; friction modifier free, diesel) is around $20/gallon, at Wal-Mart.  Whatever oil you use, check it often, to see how fast it darkens.  The SeaFoam treatment should scour the engine/transmission very clean, but if the oil darkens quickly, then change it, and the filter, again.  Cheers!

[Cabreco]

Thanks for the advice. I was planning on an oil change tomorrow. I bought the Shell Rotella T 15W-40 & filter already. The PO said he had changed the oil at the end of March and put less that 10 miles on the bike. I tend to believe him because the oil in the crankcase is nice & golden (I know the CB's turn oil black real fast, my CB500 blackend it fast) but I have absolutley no idea what he used. For all I know it can be Wolfs head econo oil, so it has to come out. The oil dampening the exhaust tip is jet black!

I don't think it caused any damage. It stalled at about 900 rpm & I guess it was just too hot to quickly restart. I did take it for a one hour ride just now at various speeds from 20 - 0 mph without any issues. And although there is still a black oil film on the tip, the bike is no longer smoking.

I think I must have a valve seal letting oil through, probably on the exhaust side. I'll tear it down this winter & do a top end. but for now I'll do the seafoam & oil change tomorrow.

Thanks again

[Cabreco]

I did the Seafoam treatment, changed the oil & filter, used Valvoline MC oil. I'll run this oil for a few hundred miles just to clear everything out then next oil change & filter I'll use Shell Rotella T.

The oil was dark but not black. I wonder if the PO used car motor oil?  2 things I did find is, when I took off the filter the PO had the spring between the filter & the block not between the filter & the finned oil filter cover. Also when I went to replace the drain plug it wouldn't thread. I found a 1 inch piece of rubber. (looked like a broken O ring) It was peeking out of the oil drain hole. I'm wondering if it was an old oil filter bolt O ring that venture in at some time. Who knows what that's from.
Looks like I do want to drop the pan & clean the oil pickup screen this winter, especially since that gasket weeps by the kickstand.
Anyway. The bike stopped smoking, & she is quieter, she even shifts nice & smoother than before.