Type of oil for a 750 twin

Hi guys. I'm trying to do my first oil change on my '83 750 LTD K1.

I had read online (bad idea apparently) that 10w30 was my best bet, so I put that stuff in. The bike ran okay at first, like crap a little later, and now won't run at all. I'm guessing it's because it does not like the 30. I hope I didn't do any damage.

So needless to say I've disregarded that questionable source and bought a user manual. When I got the manual I consulted it and it recommends 10w40, 10w50, 20w40 and 20w50. It doesn't give any guidelines to the benefits of each, it simply lists them.

Does anyone here have the same/similar bike and have any suggestions for me?

The ingredients in oils have changed over the years. For example, today's Castrol GTX oil (and pretty much all other AUTOMOBILE oil) is not the same as it was in the 1980's. Back then it worked great in KZ bikes. But, things have changed. Early AUTOMOBILE oils contained zinc phosphorus compounds (ZDDP) to protect engines from metal to metal contact. This was good for engines, but it was found to be destructive to catalytic converters. Consequently, in AUTOMOBILE oils ZDDP was virtually eliminated and replaced with different chemistry generically referred to as "Friction Modifiers." These work fine and offer good protection for normal AUTOMOBILE engines. However, today's AUTOMOBILE oil "Friction Modifiers" are destructive to wet clutches. KZ bikes (and many other brands) have wet clutches. As a result of these oil chemistry changes a distinction needed to be made between those oils which are suitable for wet clutches and those which are not. That distinction was documented by the Japanese Engine Oil Standards Implementation Panel (JASO). JASO developed a number of different oil specifications for different applications. The specifications that apply to 4 stroke motorcycles fall under the "4T Specifications." Within the 4T specifications the JASO MA class oils are specifically formulated for 4 stroke motorcycles with wet clutches.

There are synthetic, semi-synthetic, and non-synthetic oils that meet the JASO-MA standard and any of them will work ok. However, using oils that are not designated as meeting the JASO-MA standard are destructive to KZ clutches.

I have ridden my 750 twin since new in 1979. I always use 10-40 in the winter. In the summer, I use 3 quarts 10-40 and one quart 20-50.

You MUST avoid any oil which says "energy conserving" on the top as it has moly in it and that can screw up your clutch. Most 10-40 and 20-50 oils do not have moly, nearly every 10-30 and 5-30 oil does have it.

You can use "motorcycle specific" oils if you don't mind paying $9/quart. I have used car oil in mine for the entire 85,000 miles it has run. Rotella is very good (probably best value), castrol GTX is good, Valvoline is good, Amsoil is very good but pricey.

I have always run car oil (still do) and have not had clutch problems. As long as you avoid the energy conserving types, they should work.

NOTE: modern oils no longer have the additive ZDDP which all oils had back when these bikes were made. I add it to the oil. You can get it in ZDDPlus, redline break in additive, or a can of STP oil treatment also has ZDDP but will raise viscosity about 5 points (10-40 will go to 15-45).

EDIT TO ADD: syn oil is good but for bikes, my philosophy is use a good conventional oil and change more frequently. It keeps the engine cleaner and maintains the additive package in the oil. The twins were specified as 3000 mile limit for oil change interval, IMHO 1500 - 2k is a better idea. Buy gallons of decent oil at Wally Mart for $12 and the cost of changing is not that much.

Shell Rotella-T 15W-40 regular in the white bottle or Chevron Delo 15W-40 regular. Both are heavy duty oils marketed for diesel engine use & are suitable for motorcycles. Apparently, the Rotella has recently gotten the JASO MA rating for motorcycles, but I believe it's the same oil as before. They may not be suitable for cold weather, though.

What has been mentioned is good advice, however 10w30 did not cause your engine to run bad then quit, so you have more in depth repairs to do. I've run 10w30 in winter and it worked fine, 10w40 works fine. 15w40 no good in cold weather, 5w40 synthetic no good in a motorcycle. Seems like 10W40 Valvoline motorcycle oil at Walmart is a decent deal at around $2.99 quart. Of course opinions are a dime a dozen on oil subjects. I like to read over at Bob is the oil guy forums and get all the exciting details on the oil choices out there.

if it has writing on the oil cap or anywhere near there that says 10w40 I would use that.

I take all my grandsons magnetic letters off the fridge then I find all the letter z's/d's and p's and grind them up .
Thats what I add to my regular car oil to use for motorcycle oil changes. :woohoo:

I hope this is not going where I think it is.