What makes for a bullet proof engine?
A slight increase in oil capacity, with a pro-rata proportion of the oil flowing out of the motor and back in again, must surely help to reduce the oil temp? I am still working on project thoughts, via collated comments from everyone, though.
@ Steve,
Yes it does, I have an extended oil pump / filter combination and is making the colling surface bigger, but again, it needs wind to gain the advantage of the bigger area. It also contains another extra 0.3 liter oil, but that only means that it takes more time to warm up the bike from cold, and indeed it will keep the engine cooler for a longer time in the situation you describe, but it will reach the same temperatures eventually. @ Ed, My both sons (10 years old and 6 years old) own a CB72, and they will have enough parts to keep them on the street. The oldest is working together with me to restore his bike (CB72'62), the youngest is interested, and concerned about the color of his bike (it's blue, but he want's it green / orange). I hope he will change his mind when he grows older. @ GG, Very interesting and helpful info. I dismantled the carburetors and I found that the pinhole to level the pressure in and outside the bowl was closed. I replaced the little tubes since then (I couldn't get it open, just as there was never a hole), but I never had the change to see if that was the problem, since it was getting less hot in the weeks after the replacement. Jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
More 305's on the roadFor LM - I think that your strategy is working. 10 years ago I had a hard time finding ANY information or parts for my Superhawk. Through this forum, and with the help of the internet, things have really changed! In fact, my confidence in rebuilding my own bike is in part due to this forum. So I trust you feel rewarded!
@ Jensen - The time that I really vapor locked the bike was such a hot day / circumstances that most other motors would have probably burned up. I've never had any other problem with the carbs after that. I don't think it was related to venting. Thanks for the good ideas and stimulating conversation on this forum! GG Extra volume does help because there is more mass to carry the heat away and with a cooler, there is more area getting rid of heat. Jensen is right that even a slight wind helps, but even sitting still, the cooler radiates heat. so it will help - slightly.
The question for me is not so much does a cooler work and why, but "is it needed" and I have never found one to be necessary, but I don't do long miles in 40 degree C heat. All my air cooled bikes crack and ping as they cool down. Vapor lock is fuel boiled to a gas which cannot be pumped. So called because the vapor prevents fuel from reaching the carb. We don't have fuel pumps so it isn't vapor lock. It could be any number of other heat related issues and may even be fuel boiling, but that is rare. I have seen that on a race bike when the timing moved to around 60 degrees on a very hot race day and methanol was bubbling and spitting out of the vents. But the oil was still OK.. But if someone wants to fit an oil cooler it won't hurt anything.
That, coupled with the fact that there's an unsightly appendage in front of the motor, is the downside, G. I've found a nice-looking unit that will fit, and it's not a matrix -- more of a heatsinked receptacle -- so stones won't pierce it; but the unions are the weak link. Ho-hum. We'll see...... I procured a nice pair of 3k-mile immaculate PW26s a couple of years back and they've behaved impeccably; no problems with fuel delivery whatsoever. If an oil cooler is not needed on a bike, why have so many manufacturers (honda included) put them on so many models over the years? A comfortable seat is not needed, but my ass gets sore after a couple hours in the saddle. Having the timing perfect isnt critical, but I still do it.
Example: Yamaha XS750 triples did not come with an oil cooler, and had issues with big end bearing failures. Yamaha added the cooler to the XS850 triple stock, and improved the oil ports to big end bearings. Fixed that problem. Oil coolers are also an excellent idea if you are oversizing pistons, since the reduced cylinder wall has less mass to soak heat. I prefer to mount the cooler high to keep it away from the road. If you dont like how it looks, build an aluminum sheetmetal shroud to help hide it and paint it. the shroud will help baffle air through the cooler. Plus the shroud is a good place to put custom owner logos. It can also be a way of adding a spin on filter to the oil system. For any dry sump engine the simplest bolt on upgrade usually is a larger oil tank. '61 CB77, '72 TC125, '72 CB350F, '73 CB350G, '76 CB400T, '79 XR80, '79 XS750 (850), '83 CB650S, '84 KDX250,'91 YZ 250
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