Engine troubles

Hi, hoping to get some thoughts on what could be wrong...

One month ago, i finnished the engine overhaul on my z500 B3 and ended with filling up with new oil.
Since I had changed all seals, and synthetic oil was easier to get, i chose synthetic 10w40 oil according to the manual.

I quickly noticed bad performance and clitch slippage. 2 weeks ago i got myself some castrol oil for vintage bikes, real mineral oil which I was recommended from a facebook group to use.

After the oil change, i now have troubles starting the bike. To the point where i drain the battery and have to push-start the bike.

I also suspected that the carbs drew extra air from somewhere, but using some start gas (uhm.. thats what its named here. Feels wrong saying it in english. Hope you get what I mean anyway), didnt make a change. The engine is not affected in any way (except if sprayed directly on the airpods, which makes the engine stall).

If the bike is left in direct sunshine it starts easier, but not easy.

At the moment, there are, since the previous owner, mounted pod filters on the carbs.
I will soon mount an original airbox, as soon as the brackets finds its way to me from the US (should be during the next days).

But anyway, having to constantly use starting gas and push-starting the bike sucks. What could be wrong?

The sparkplugs are good. I tried at first changing them (NGK DR8EA). The engine refused starting with the new plugs, so I reverted back to the old ones.

Also, I got some idle problems where idle can go up to 4k rpm when the engine is hot.
This is one of the reasons I am changing to original airbox instead of the pods.
This got slightly better after the oil change though, but it is still a problem.

Fully synthetic is known for causing clutch slip and the Castrol mineral may well be a mono grade and too thick creating drag on the crank etc when cold hence it being easier to spin when left in the sunshine where the engines bulk has warmed in the sun and hence thinned the oil slightly.
Get some semi synthetic Silkolene super four or similar 10/40 in it before you do anything else.

Exactly what oil did you use? If it did not have "JASO-MA" as one of the standards it met printed on the label it can easily make the clutch slip. JASO-MA is the standard that shows the oil is safe for wet clutches. That standard came about long after the manuals were printed because oil companies changed their formulas to ensure the oil would not damage catalytic converters on cars. Full synthetic works fine in bikes with wet clutches IF it meets JASO-MA standard. I've been using Mobil-1 Racing 4T full synthetic motorcycle oil for 9 years with no problems, but do NOT use Mobil-1 CAR or any other synthetic CAR oil. Ed

see: mobiloil.com/en/motor-oils/mobil-1/mobil-1-4t-motorcycle-oil

The problems you reference, other than the clutch slipping, has nothing to do with the oil. The air/fuel mixture is jacked up because of the pods. I'd pull the carbs and clean them and take a full inventory of the jet numbers, comparing them to the numbers in your service manual. Put everything back to stock. Then put the stock airbox back on and make sure you don't have any intake leaks. That creeping idle is due to a lean condition which suggests vacuum leaks.

The R in DREA is for resistor, and you shouldn't be running resistor plugs. Look in your service manual and get the proper plugs.

Oh, and while you are waiting for your airbox parts to show up take some time and check valve adjustment. This is a critical step in getting your bike up and running and failing to keep the valves in spec will result in damage to the engine, in addition to poor running.

Good luck

In all honesty, i do not remember if it was JASO-MA, but the oil was sold together with an oil change kit (filter, gaskets and oil) specified for Z500.

Then ofcourse, i expect they sell the cheapest oil that would fit for any motorcycle.
The oil used was "Motorex Formula 4T 10w40".

The castrol oil i changed to was indeed single grade oil.

Thank you for your answer nessim, I have been thinking exactly the same.

Regarding the plugs, i see, didnt know the R was for resistors, which ofcourse is wrong.
I will order new ones.

The reason for the winter overhaul was to check the valve clearances and they have been shimmed to spec according to the manual.

I just had a suggestion from a friend, to drain a third of the mineral oil and put in some semi synthetic oil and mix that way.

I got about 1 liter left of the earlier used semi synthetic oil. What do you guys think? Inadvicable or a good try?

Why am I even considering it?
Because I have during 2 moths time bought 8 liters of quite expensive oils (where the current castol was the most expensive ofcourse).

If adviced to do a complete change, i will, but i would much rather save some money if I can.

I may have misundertood your post, but If you put in single grade oil take it out. That is not appropriate at all for your bike. Ed

My apologies, no, it is not single grade....
Castrol Classic XL 20W-50 (multigrade) 4.54 liters.

Carb holders leaking.
Steve

swest wrote: Carb holders leaking.
Steve

I have looked at that, and I cant find no leaks at all.
When it comes to that, i suspect the pod filters which is why I will change to stock airbox.

While running spray carb cleaner where they bolt onto the head. If there's a change, they have to be replaced airbox or not.
Steve