137 replies to this topic

[Studley Ramrod]

Been busy trying to iron out an annoying splutter I'm getting when I hold the revs at 2000-2500rpm. Weird thing is it doesn't always happen.

My first attempt was to fettle the pilot screws and balance the carbs, I saw some improvement when the bike was stood and thought I'm in the right area. But, the carbs weren't equally balanced and yet were running smoother.    After taking the bike for a blast since then I'm still getting the splutter, although it is smoother below and above 2000-2500rpm.

 

Sooooo, far from content, I whipped off the carb tops today to inspect the needles and found this.

 

 wornbit.jpg   45.2KB   2 downloads

 

The needle has been worn by the steel washer.  Thing is, where the needle and washer sit in the slide, there's a semi-circular step, also the washer centre hole is much bigger than the needle width, so what can happen is the washer tilts on the needle and prevents it from moving smoothly.  Now, according to Factory Pro, this type of wear should not affect richness. Thanks to a certain Allan Eccles.  http://www.factorypr...ch/needle1.html  Given that I can't get hold of a new needle until after new year, I've decided to fit a smaller diameter washer and place it inbetween the clip and the plastic noggin, loike this.

 

 wornbit1.jpg   50.06KB   0 downloads

 

Another thing that's long bothered me is, the Haynes shows the metal washer in the position in the first pic, whilst the Yamaha farts pile shows it positioned as in the second pic.

 

Anyhoos, I'm now gonna refit it all and see what happens, if ya see a puff of smoke on the horizon please ring the ambulance for me, ta.

[Apache]

Either Haynes or yamaha are obviously wrong and I wouldn't automatically curse Haynes. I've worked for several hgv dealerships on and off and they all drop the odd clanger in their workshop information systems. I'll follow the posts that follow. Pretty sure mine are as per Haynes. But which is correct ?

Edited by Apache, 24 December 2016 - 02:39 pm.

[Got1now]

Well spotted Ian, hope it sorts the problem. My needles were set up like yours, with the nylon washer at the top, whether that was original or not, I've no way of knowing. The washers on mine were a fairly good fit on the needles, so maybe a set of the correct diameter washers might be worth a try.

Good luck anyway.......If you want to try a set of needles from mine before you buy some, let me know, you're welcome to borrow mine and see if it does the job.

[Studley Ramrod]

Either Haynes or yamaha are obviously wrong and I wouldn't automatically curse Haynes. I've worked for several hgv dealerships on and off and they all drop the odd clanger in their workshop information systems. I'll follow the posts that follow. Pretty sure mine are as per Haynes. But which is correct ?

 

It doesn't seem to make any difference tbh.  I guess the yamaha way cuts out the needle wear. 

 

Well spotted Ian, hope it sorts the problem. My needles were set up like yours, with the nylon washer at the top, whether that was original or not, I've no way of knowing. The washers on mine were a fairly good fit on the needles, so maybe a set of the correct diameter washers might be worth a try.

Good luck anyway.......If you want to try a set of needles from mine before you buy some, let me know, you're welcome to borrow mine and see if it does the job.

 

Cheers Pete, I've already got some spare mk2 needles but they're a different profile to mk1 wans. 

 

Well, fitted smaller washers to both needles and still getting the splutter.  Looking down at the carb inlets and it's no1 carb thats spluttering.  Couldn't tweak it out with the pilot screw.  Ended up removing the carbs for inspection. Checked the vac pipe for holes, checked the diaphragm, and have just removed the inlet to see if the gasket is good, which it is.

[Got1now]

I know you'll think I'm taking the p**s, but,...... have you tried swopping plugs?........just to eliminate them.....either as a pair, or from side to side, see if the problem stays on No1?

[Studley Ramrod]

I fitted a new plug to no1 cyl the first time, didn't check the cap or coil though.  Just seems odd that it's only spluttering at 2000-2500 rpm.

[TinTin]

My commando had that fault and the slides were worn. Prob disappeared with newer carbs.Sorry.
I also had a 250 Honda doing similar but dropping the needles a notch sorted that one.

[Studley Ramrod]

New sliders are mega bucks but I could try swapping them over.  I could try dropping/raising the needles but doing that doesn't really identify the cause of the problem.

Gonna strip the carbs down and give them a blast with compressed air, also gonna check the jets that are checkeable.

[fixitsan]

I'ld spend a few minutes checking the connectors to the coil. There could be a very specific vibration causing a loose terminal to vibrate just enough.

[Apache]

Give fixitsan suggestion some thought Ian. The vibration pitch at 2 to 2500 could be causing a loose terminal. I've had success in the past tracing fuse blowing faults by setting the revs at the problem causing pitch and slightly moving harnesses and plugs etc around to see if the fault clears. Bonne chance

[Studley Ramrod]

I'ld spend a few minutes checking the connectors to the coil. There could be a very specific vibration causing a loose terminal to vibrate just enough.

 

The mk1 only has the one coil for both plugs so doubt it's a coil connection as it'd also cause a fault with the other pot.  Could be something similar happening to the plug cap or HT lead though.  I've checked both leads and plug caps in low light for shorting but couldn't see any sparks.

[Apache]

[quote name="Studley Ramrod" post="343294" timestamp="1482593717"]
It doesn't seem to make any difference tbh.  I guess the yamaha way cuts out the needle wear

Mk2 factory manual has washer between circlip and plastic widget. Makes sense because it'll stop the smaller circlip cutting in to the plastic. I'll have to check mine now 🤔

Edited by Apache, 24 December 2016 - 08:41 pm.

[Studley Ramrod]

Well, having the best Xmas ever here, fettlin' me carbs

 

Thought I'd check the fuel levels even though I'd done them a year ago and......fookin' no1 cyl is way over.  How did that happen ?  Soooo, now adjusted and will fire it up once I've done the festive taxi with a wiff of petrol run.

[Got1now]

Hope you've got to the bottom of it. Keep us posted as to how it goes. Glad to hear you're enjoying yourself on Xmas day!!!!

[Studley Ramrod]

It was still spluttering but I managed to minimise this by outing the pilot screws to just over 4 turns, will go for a blast later to see how it copes under load.

[wicklamulla]

any exflanation as to why the fuel level could have changed Ian ?

[TinTin]

Have you checked the resistance in the plug caps Studley

Edited by TinTin, 26 December 2016 - 01:09 pm.

[Studley Ramrod]

any exflanation as to why the fuel level could have changed Ian ?

 

Not really Ken, it's a mystery.  Bike's been stood for a year with just the occasional start up so maybe something to do with that ?

 

Have you checked the resistance in the plug caps Studley

 

As we speak Sam, just removed the coil and caps etc.  Caps ok, coil secondary resistance test ok, coil primary resistance not quite ok. Should be in the range of 2.38 - 3.22 ohms and I'm getting 3.50 ohms.  Now wondering if that's why I'm struggling to set the carbs up properly.

Went for a blast today   It's pulling like a gud un most of the time, even managed to hold 2000rpm without a splutter for about half a mile, then it spluttered.  A few blips on the throttle and it cleared up.    I'll get there eventually.

[fixitsan]

Very few meters would be able to differentiate between  3.22 and 3.5 Ohms.... I think you're in the right ballpark

[celticbiker]

Could it be running a bit rich in that range for whatever reason and a slightly colder plug might just run hot enough to overcome it?