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Oil Cooler & Temperature questions

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  • Oil Cooler & Temperature questions

    Since these Kats are oil cooled I was wondering if it might make sense for someone doing a lot of stop and go (city) riding to upgrade say....a 600 bike to a 750 oil cooler, or maybe even put a couple 600 oil coolers inline just to try to keep the bike cooler since it won't be getting much airflow in stop and go traffic.

    Can these bikes overheat? I mean, if I just turned my bike on, and let it idle all day it's not getting any airflow from riding. Or what about sitting in stop and go traffic. -- I can often feel intense heat radiating up from the engine while sitting in static traffic, which means the cooling fins are working.
    Sometimes while stuck in traffic jams I just shut it off....then walk it up the sidwalk if I'm not far from home ...which is sometimes faster than waiting behind the trapped cages.

    Would it make sense to run a larger cooler, just to keep the engine running cooler overall? I would think that this would keep the cyls cooler, which increases oxygen density...which would increase overall hp...right? or wrong? or would this have an adverse effect on the engine not reaching proper engine temp (always being too cool) -- is that possible?

    Any thoughts?

  • #2
    You certainly could upgrade to a 750 oil cooler, and it wouldn't be to hard either. The most you may have to do is move the bottom brackets of the oil cooler. Other wise its really only a matter of undoing a few bolts.

    As for overheating, from what I understand, it is not such a problem with the oil cooled Kats, even in the hot Florida and Arizona heat.

    I am sure more could chime in with better info. As for the cooler swap though, it would be pretty easy. Adding a second oil cooler would be a lot harder though.
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    • #3
      (A) The quality of the oil is much more important than the size of the cooler above stock. Standard car oils are not designed to hit the type of temps the Kat's oil can hit, and experience high amounts of evaporative volume loss. Look for oils which are both JASO-MA rated, which limit the evaporation rate over the lifespan of the oil to 20%, and which also have other qualities that will fair much better running at 280 - 350 degrees (F) active temps. Not all oils shed heat at the same rate, and one of the reasons I do use the GPS is because it shed heat in my informal tests better than the other choices I've tried (unfortunately, it also makes the cooler produce more heat on hot days; I'm just happy there's no radiator fan blowing that heat over me).

      (B) The only reports I've heard of overheating kats were always high speed highway travel followed by traffic jams at idle for extended periods in very hot (90+ weather) using low-quality oils. Switching to the JASO-MA rated oils removed the problem. My golden rule is if you would feel uncomfortable standing barefoot on asphault, switch up to a 20w50 for that season (still a JASO-MA rated 20w50).

      (C) I live in Florida, often drive triple-digit speeds and then come off the interstate into urban conjestion. I haven't had any issues with the stock cooler using Castrol GPS 10w40 and 20w50 (both JASO-MA rated). There is a wide variety of oils that meet that rating, including Castrol ACT/Evo, Castrol GPS, Royal Purple CycleMax, etc, etc -- just be sure the bottle says it plainly in the ratings that is JASO-MA rated (and not just that it "exceeds JASO-MA friction ratings", which is a marketing ploy).

      (D) To install the 750 cooler on the 600, the lower mounting tabs need to be cut away and rewelded to support the different positioning on the 600's frame. You can't fit a second 600 cooler into the set-up (insufficient space front-to-back, and if you put it below the stock cooler, it'll be exposed to the exhaust header heat too much at stand-still).

      (E) I'm working on licensing a set of oil temp senders & gauges suitable for the Katana, Bandit, etc. These will be weatherproof, anti-fogging, vibration resistant, etc. and have a temp range that exceeds the Kat's high active temps on hot days. If you get one, you'll know if the oil is getting way too hot.

      For more on selecting oils for the Katana, Bandit and other motorcycles (especially air-cooled and oil-air-cooled bikes), see:
      CyberPoet's "How to understand and choose motorcycle motor oils" at

      =-= The CyberPoet
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