Power valve adjustment newbie

[nobby62]

Just a quick question for the ypvs experts. I am new to LC’s and YPVS’s... I have been checking the ypvs adjustment today using the haynes manual as reference...... Its similar to the RC valve on my NSR so I’m familiar with the principle but the setting up procedure is different.
First thing I did was take a picture of the valve position after the servo has cycled when the ignition is switched on.... this is how it was lined up:

its almost a full hole out..... So i removed the pulley because I wanted to make sure that it wasn’t fitted 180deg out as I have heard it’s possible to do on the yamaha (not possible on the Honda).... but there is no obvious indication that it is in the correct position and can be spun right around. So in the manual it says “turn the power valve assembly so that the screw heads on the curved joint face upwards”...well this got me stumped straight away...  
1st question, eventually i found these which I assume it is referring to?

So if thats correct then the valve was the right way round but just out of adjustment....so I followed the procedure and locked it in place with a drill and adjusted the cables until it lined up correctly after switching the ignition on and off...
So the 2nd question, would the ypvs experts expect that amount of adjustment error to cause running issues....I have a spluttering missfire at higher revs when under load. The engine now starts up with half a kick and picks up really quickly and revs and idles perfectly. At the moment I cant give it a proper road test as it has no MOT.... I'm hoping the adjustment will have cured the miss-fire, I’ve been through everything else....

[midlifecrisisrd]

1) yes that's the screws they are talking about

2) not sure. It may be too rich up top and sputtering if the valve isn't opened fully.

What pipes/carbs/jetting/air filter are you using

Steve

[nobby62]

Thanks Steve.. the engine is standard or so i am informed by the po... the carbs are standard setup except for the main jet which has been increased to a 210 (std is 185). This is because it has JL pipes fitted although I have never ridden it I am informed that it has done a trackday and ran well and looking at the tyres is wasn’t hanging about.. The airbox is standard with an oiled foam filter..

[midlifecrisisrd]

Should be fine then

I was more concerned you may have been using pod filters as f2 carbs don't like them

Steve

[nobby62]

Cheers...I’ll try to book in for an MOT tomorrow and see how it goes..... at least I’ll be legal for the road test..

[coose]

Now then Rob,

Although the power valve looked to be out of line, it was set up correctly with fingers up the exhaust port. I never trusted the markings and I was right! 
With it set up like that and as you received the bike it revved beautifully right through the rev range on the 210 mains and having done many plug chops it looked perfect (i.e. a safe ginge), so I don't know what's going on there.
Did I read that you had the carbs cleaned? Maybe there's a bit of crap stuck in a power jet tube?

I didn't do a track day on it, just ran it in for 300 miles and did another 300 miles on the road. The front tyre was an almost new part-worn picked up. The rear was brand new though (and hideously expensive!).

The air filter is a genuine Yamaha item.

[muttsnuts]

Rob, I owe you a few pints, so just bring it across and we'll fix it on the dyno, just give me a call and we can arrange, saves any guess work

[nobby62]

Hi Ian, my apologies regarding the valve setting, I’ll stick my fingers up there and have a feel myself....i was just looking for anything that could be the issue. As it happens I took her for an MOT this morning, which she flew through, but the running issue is still there..... she runs ok at virtually closed throttle and low revs and will rev through to about 6k on a flat road...but as soon as i open the throttle she starts to splutter and missfire.. plugs look perfect, checked them just now.... she starts idles and revs up beautifully....so a bit of a mystery. As you say it could be a blockage somewhere, i have cleaned the inside of the tank with some rust remover which does tend to leave some loose particles which I have tried to swill out but could be the problem. I have had the carbs apart a few times and everything is std except the main jet as you say.... the floats were a bit high and i set them back to 21mm but then i had fuel leaking from the overflow....so i put them back to about 23mm which is about where you had them and now it doesn’t leak.
Dave, Thanks I will give you a call to discuss, i don't like to be beaten but as you say, without diagnostic equipment its all just guess work.... cheers

[midlifecrisisrd]

23mm float height will reduce fuel level by 2mm

It should be fine at 21mm

If it's overflowing at s1 then the fuel valves need changed

Steve

[nobby62]

They’re brand new Steve....from Norbo.. I’ll be back into those carbs again this afty for another rummage... ‘kin 2 strokes...🙄

[coose]

It's not a problem Rob, it certainly sounds like something main jet related. I'd certainly have a good look at the carbs before taking it to Dave's to save time whilst you're at his.

Have you tried a fresh spark plugs? They were new when you bought the bike from me (bought from my local bike shop so they're definitely genuine), but if you've been firing it up in the garage a lot it could be that one is starting to foul.

I'd fully intended nipping it down to Dave's as the jetting wasn't far out but I thought he could certainly work his usual magic!

I'm glad it flew through the test though, not that there's any doubt it wouldn't as anything that could move was brand new.

[nobby62]

Hi Ian. Yes the bike is spot on... all i have done is cosmetic and even then it didn’t need much... I was sure it seemed carb related but I’ve just had them off again and checked everything, put it back together and exactly the same. I did buy some brand new plugs from halfords so I’m sure they should be ok, plugs are usually my first port of call on running problems.... I’m a bit perplexed on this one.. it seems fuel starvation but the vent seems ok... Might have to admit defeat and get magic Dave to look at it...

[coose]

Hi Rob,

Your problem is niggling the hell out of me as the bike was as sweet as a nut and I lost a lot of skin building it, and if the carbs look to be fine I'm wondering if it's something else.

I think it's worth checking the resistance of the two magneto coils on the stator as it could be that the high speed winding is failing. The stator is the one that came with the bike so it's probably original and it's not unknown for them to fail - I had to replace the one on my KR-1 not long after I bought it as one moment it was fine, the next there was no spark as the low speed coil had failed. It was an easy fix, £115 for a new stator from Electrex World.

It's worth checking - the resistance values should be in the manual.

[muttsnuts]

its fixed, needs some new carbs, for now Rob's running on my test carbs

[coose]

Did you find what's wrong with the existing carbs, Dave?

[muttsnuts]

Jun 20, 2020 21:55:48 GMT 1 coose said:

Did you find what's wrong with the existing carbs, Dave?

nope, but they are buggered for sure, fitted my speare set and the bike runs spot on

[coose]

Strange, it was running well on them....

[nobby62]

Jun 19, 2020 14:19:58 GMT 1 coose said:

Hi Rob,

Your problem is niggling the hell out of me as the bike was as sweet as a nut and I lost a lot of skin building it, and if the carbs look to be fine I'm wondering if it's something else.

I think it's worth checking the resistance of the two magneto coils on the stator as it could be that the high speed winding is failing. The stator is the one that came with the bike so it's probably original and it's not unknown for them to fail - I had to replace the one on my KR-1 not long after I bought it as one moment it was fine, the next there was no spark as the low speed coil had failed. It was an easy fix, £115 for a new stator from Electrex World.

It's worth checking - the resistance values should be in the manual.

Hi Ian, sorry i missed these last few posts.... As Dave says, there was a problem with one of the carbs. The air/ fuel ratio was miles out and we couldn’t get them anywhere near the same... put a spare set on and ran great straight away. So now waiting for some replacements to arrive. Then i will get the old ones and go over them with a magnifying glass to see if i can find the problem.

[coose]

Hi Rob,
That's certainly reassuring that you found where the problem laid, and that it's easy to fix. I can only imagine that there's a bit of muck in a PJ or maybe an emulsion tube from what you say, and you should know which carb since Dave has had his AF meter on it.
Did you have a spin on it with Dave's carbs fitted?

[nobby62]

Hi Ian, the problem was one carb being way too rich i.e. delivering too much fuel rather than being blocked. With the air filter removed that side then leaned out and ran whilst the other side became way too lean....we couldn’t balance them out. So when I inspect the carbs I will be looking for excessive wear perhaps around the emulsion tube bore.....? Something that could lead to excessive fuelling. Don’t worry about it though, everything can be sorted. I have ridden the bike a couple of times now and she works well albeit in need of fine tuning the carbs which we didn’t bother as they are only on there temporarily. The only other issue is the clutch that is dragging a little and making it difficult to engage neutral once warmed up, I’m hoping that can be sorted by adjusting the mech inside the clutch cover. Other than that she is great and I am very happy 👍.

[coose]

That's quite strange, I expected it to be lean rather than rich, but better that way than the other. I'm glad you're happy with the bike otherwise, and as you say it's easily sorted.

The clutch friction plates are new, as are the springs (both EBC). I think I fitted new steels but I'm afraid I can't remember, but I did refit the o-rings between the plates so you can probably lob those which should help.

[nobby62]

Thanks Ian....I’ll have a look when i get round to it.....its rideable so no massive rush, plus I need to order some gaskets first.