Yamaha running sluggish

[Iggy]

I have a 1991 Yamaha 400 Diversion road bike, started the bike after had choke on, then proceded down the road when the bike felt it was running on 3 cylinders. It sort of missing when you give it some throttle, eventually made it home and had a look at all 4 spark plugs, they were quite black so gave them a clean with a fine wet and dry paper. put the plugs back in and took her 4 a spin down the road and have the same problem. I did give her an oil change the other day and she does run on 91 octane fuel.
Does anyone have some helpfull advice that would be very much appreciated.
Cheers Iggy
ps the bike was running sweet as prior to todays incident.

[Max Preload]

I have a 1991 Yamaha 400 Diversion road bike, started the bike after had choke on, then proceded down the road when the bike felt it was running on 3 cylinders. It sort of missing when you give it some throttle, eventually made it home and had a look at all 4 spark plugs, they were quite black so gave them a clean with a fine wet and dry paper. put the plugs back in and took her 4 a spin down the road and have the same problem. I did give her an oil change the other day and she does run on 91 octane fuel.
Does anyone have some helpfull advice that would be very much appreciated.
Cheers Iggy
ps the bike was running sweet as prior to todays incident.

Have you been riding on reserve lately or left it out in a heavy rain?

[Iggy]

No mate I always garage my bike and havent touched the reserve for at least 2 weeks so yeah am a bit worried about what the problem is.

[Katman]

Do you start the bike with choke and leave the choke on for a while and then only do a very short ride before turning the bike off?

[CookMySock]

is it possible you overfilled it with oil ?

DB

[Iggy]

Do you start the bike with choke and leave the choke on for a while and then only do a very short ride before turning the bike off?

I start with choke on and once it is warm enough I turn choke off then I proceed on my ride, I do about 10 ks to work.

[Iggy]

is it possible you overfilled it with oil ?

DB

I put in exactly the required amount which is 2.2 litres.

[CookMySock]

I put in exactly the required amount which is 2.2 litres.

ok. If it were me, I would find an alternate method to double-check this. Is there a sightglass window, or a dipstick ?

How many km do you travel before you turn the choke off ?


DB

[Iggy]

ok. If it were me, I would find an alternate method to double-check this. Is there a sightglass window, or a dipstick ?

How many km do you travel before you turn the choke off ?


DB

Its got a sightglass window but cant see any oil so I may have overfilled the bloody thing. And I dont ride with the choke on as I usually like to let the bike idle with choke on before I hit hit road.

[xwhatsit]

How many km do you travel before you turn the choke off ?

Surely the answer for that should always be 0km? I fail to see how running with an intake restrictor and super-rich running is in any way healthy. Don't be lazy, it's not like it takes long warming up enough to run sans-choke.

Over-filling it might be a possibility -- it takes 2.2L, but it's bloody hard (especially with a cold engine in this sort of temperature) to completely drain all the old oil. I know I can only squeeze 1.5L-1.6L in (1.7L recommended, 2.0L from case-apart rebuild), despite tipping the bike over on its side and giving it a brief ride beforehand to get the oil nice and runny.

If you think its running on three, you can check which cylinder is dropping by dropping some water on the headers with a teaspoon or something. Get it hot, then see which headers are sizzling and which are not.

[Iggy]

Surely the answer for that should always be 0km? I fail to see how running with an intake restrictor and super-rich running is in any way healthy. Don't be lazy, it's not like it takes long warming up enough to run sans-choke.

Over-filling it might be a possibility -- it takes 2.2L, but it's bloody hard (especially with a cold engine in this sort of temperature) to completely drain all the old oil. I know I can only squeeze 1.5L-1.6L in (1.7L recommended, 2.0L from case-apart rebuild), despite tipping the bike over on its side and giving it a brief ride beforehand to get the oil nice and runny.

If you think its running on three, you can check which cylinder is dropping by dropping some water on the headers with a teaspoon or something. Get it hot, then see which headers are sizzling and which are not.

Will have a good look at the bike over the weekend and may have to drain some oil and give the bike a run. If that does not do the trick then will check on the headers.

Thanks Iggy

[CookMySock]

Its got a sightglass window but cant see any oil so I may have overfilled the bloody thing. And I dont ride with the choke on as I usually like to let the bike idle with choke on before I hit hit road.

ok, coolies. Riding with the choke partly on for two minutes won't foul an engine, but idling for more than a few minutes with the choke on full WILL foul an engine.

There are many many personal preferences to warming an engine, and you should probably just use yours, but for your reference, I do the following - Full choke, start, run engine until revs stabilise (10 seconds ish) and then choke back gently until revs just start to drop off and leave for 30seconds, OR choke back until about 2,000rpm and ride it off. Choke off fully in the next 2mins or less if on the open road. FYI

Surely the answer for that should always be 0km? I fail to see how running with an intake restrictor and super-rich running is in any way healthy.

No. There is a whole thread on this topic. No one is suggesting riding with the choke full on. ALL modern fuel injected cars and bikes partially richen the mixture when the engine is warming, and THAT is what the choke is FOR, not just to get it started initially. If you don't richen the engine when cold, it will falter on you at just the wrong time, and well, you know the rest of this story.


DB