New bike to me running issue

[Captbarb]

Hi I'm new to mz and the forum got my 42 year old bike running only done 630miles tank and carb cleaned idles ok but on my test drive pulls good will cruise at 60 mph but wot it almost dies exhaust splutters and starts slowing down I had two strokes when I was sixteen along time ago any thoughts on this .

[breakwellmz]

Blocked fuel tank filter or filler cap vent?

[Captbarb]

On my test run I pulled the fuel cap and I can blow through vent hole so maybe your right fuel tap I will evestigate somebody suggested de cokeing the exhaust so I've done that aswell.

[Captbarb]

Well after a new exhaust and a fuel tap my reving past 5000rpm still exists.
So start up idle low and mid range it's really good the plug was chocalate brown last time I checked could I have a problem with my points maybe .

[breakwellmz]

Pop the air filter off and see how it runs, it won`t do it any harm for a short time.

[Captbarb]

Ok will give it a go you think it's to rich at the top end ?

[Blurredman]

For what it's worth, my '87 ETZ250 doesn't want to rev much past 5.5k. Though, it has a 76mm piston in so always attributed it to the port timing being off potentially. Or maybe weight of the piston or something.

Youre's is unchanged? My 251 will go to 6k no problem. I can cruise at 70mph on that no problem. But I can't really use the ETZ250 (295cc) above 60. 65mph in short burts for overtaking and moving back into lane one. I do have an 18 tooth sprocket on it, and have done for several years but thinking of going back up to 19tooth to circumvent this rev problem.

[Captbarb]

What would be the correct position on the needle on the main jet did they have it lowerd for running in ,just thinking seems my bike only had 630miles maybe it's set to low will check tonight .

[Blurredman]

The lower of the two tangs should be in the middle position. It can be raised for running in. For many years I used to use the raised position but now I use standard.

[Captbarb]

The issue was the fuel level was to high in the carb adjusted all good tried needle at highest position ran ok plug looked a little rich it's now been moved down one notch but yet to road test .

[Chris W]

I've just fixed the same issue on my ETZ 251 (BVF carb). One of the original brass floats was taking in fuel through a tiny hole, resulting in an overly high fuel level and rich running. I tried replacement plastic floats but they were heavier than the OEM brass floats so a little tricky to setup ............and then over a period of a week or so they absorbed fuel and so became even heavier and hence wrong fuel level again .........so I replaced with a new brass float and all is well.