YZ400E

[Scott W]

Hi All
I have a YZ400E (1978) and it loads up a little at high RPM and takes a while to clear. Fully rebuilt engine including carb using standard jetting. I think it may run better with different oil and fuel/ mixture so I was wondering what others think about fuel/ oil ratio and type of oil and or fuel additives? Going for a ride this weekend to see if I can get it running better. Any feedback would be great:)
Scott

[shelpi]

get the SUDCO 5th Edition Mikuni tuning manual its the bible all you will need for you and ya mates for the rest of your Life!

[80-85 husky]

maxima 727 castor at 30:1 should be all you need. smeelllss so good (when your second) air filter clean? muffler freshly packed?

if your talking about the start up missing and clearing out till it warms up, all two strokes do that and dont worry about it.

if it does it all the time then try this...

sounds like your needle clip needs to be dropped 1 notch or lifted 1 to clean it up. if it hesitates or feels like its dragging a bit as you open up, the needle clip may need lifting 1 to lean it out a bit.

if its missing a bit as your roll on the throttle a bit, it may need lowering 1 clip to richen the mix going on to your main jet.

[bigk]

Nothing to do with what fuel ratio or brand of oil you are using IMO. Standard jetting is a good starting point but every engine is different. You need to do some due diligence & spend the time & effort to jet it properly. Your problem is in the jetting (IMO) & the first thing I would do considering the symptom you describe, is come back a couple of main jet sizes. It takes some time to sort jetting (if you are fussy) but the result is worth the effort. Dyno runs are OK but not the "be all, end all", my feeling is it's best to do it in the dirt as you will be riding it.
K

[Slakewell]

To many things could be wrong.
1) Are the reeds OK , Highly recommend V force reeds?
2) Is the pipe and muffler clear and the correct type? Try a test ride with no muffler.
3) Is the carby slide worn and allowing air to by pass? New carbies are cheap.
4) Is the ignition timing correct and the advance working?

There are many threads on here in regards to fuel/oil try the search. 

[shelpi]

Sudco will help with diagnosis, but do get the manual for your bike, would also recommend 2 stroke tuning ie Graham Bell two-stroke performance tuning these will give you specifications, std settings, diagnosis and tuning tips tricks and hints, and you are at the right place here these guys have a lot of experience/knowledge