Ypvs running issues - sorted

[robw]

Hi, just built the Gamma and have running problems with the engine.
It starts fine and runs in the garage fine, although the revs did take time to return to normal. That was sorted by turning the air screw out and changing the pilot valve.
It has Kenny's pipes and foam air filters fitted, rest is standard.
Main jet - 280
Pilot jet - 25
Needle - 4 from top
As you pull away it gradually dies and unless the choke is pulled out it comes to a halt, regardless of throttle position.
If you ride it with the choke on it rides normally.
I think it still needs a bigger pilot valve, but that is a uneducated guess.
I have checked all the drillings in the carbs and have the float valve height (21mm from gasket face) .
Any ideas from the more savvy people out there.
Cheers Rob

[Yogi]

Hi Rob have you got balance pipe on between the carbs? Have you blocked the vacuum hole on inside of right carb.? Are the float bowls on the correct carbs ? Have you blocked the 2t oil pipes on the bottoms,if not used ? Are there any air leaks ?

[robw]

Hi, balance pipe on, oil pipes in use. I have put a tube on the vacuum pipe with a screw in the end, held in with a clamp.
I will check the float level using the tube that is attached to the float bowl drain.
I will let you know how I get on
Rob

[midlifecrisisrd]

Hi,

I'd say you are too lean. on the pilot and maybe on the main. What carbs you running?

Thought YPVS carbs used a 27.5 pilot as standard. I used 260's with an airbox so you may be better starting at 300.

Steve

[paulo]

What carbs and engine are you running - as each type of carb have certain basic setting as a start point.

[fatfastroger]

Kenny advised me to use 290 mains with standard airbox (snorkel removed) so I'd say you're running a bit weak,esp with pod filters. I have yet to get mine running but have 31k engine and carbs with Kennys pipes. Pilots are 22.5 standard. If the air screws are roughly 1 to 2 turns out and it starts and idles then surely the pilots are in the ball park ?
Pulling the choke will richen the mixture so maybe that confirms either main is too small or you have an air leak.

[steeley]

check the emulsifier tube ,the brass tube that the main jet goes into.does it have a raised shield on it or is it flush with the carb.if it has a shield then they a ledar items .if so put the clip in the lowest groove to raise the needle.had a similar problem years ago, bike would not pull off .raised the needle and bike would pick up ok.my tzr 350 ypvs 31k engine kennys pipes ramair foam filters 290 mains colour looks good on the plugs oh and home made boost bottle made out of copper pipe.

[robw]

Hi, I have 31k00 carbs fitted, so standard jets are 260 and I went two up to 280. I will go up to 300, It does cough and splutter when I open the throttle so I will play with the main jets as well.
Cheers Rob

[robw]

It does have the raised shield emulsion tube as well, so I will put a bigger jet in first then play with the needle
Rob

[andreas67]

I am running main jets 280 with TSA pipes and pods and the needle is 5th groove from the top. This did enrich it when running part load, this was clearly visible on the exhaust temp (lower).

[steeley]

rob, sounds like you are going in the right direction hope you have it sussed soon .

[fatfastroger]

let us know how it ends up - no 2 engines will be the same, better to be slightly rich, till you can plug chop at full gas

[midlifecrisisrd]

OK I stand corrected, 22.5 pilot is standard ( I said 27.5 ) knew it was something .5 lol.

At risk of getting it wrong again the 31k carbs were 240 mains as standard so you are 4 sizes up.

Steve

[robw]

Finally a big improvement. I have accurately set the float bowls as they were out, using the blow down a pipe until you feel faint method. I have also put a 330 main in, which I will replace with a 300 to see if it runs well still.
Air screw is all the way in, so I will fit a 27.5 to enrich the slow running circuit(that's the correct way?)
It hunts at 3000 revs, so hopefully this points to its still running lean
Rob

[fatfastroger]

glad that you're getting a result, 330 main ! Must be a big hole !

[robw]

After the previous adjustments, as I blipped the throttle, the revs would become uncontrollable. So after a good check, I could see no leaks and have returned to a 25 pilot jet and 300 main, so I will see what this is like.
If all else fails I will go back to the previous adjustments where everything ran well.

[robw]

That's what I thought, slides work well as I checked them before and after. As for the leak it has new carb rubbers which are tightened, I have checked the vacuum pipe and ensured that its still sealed.
So running out of ideas
Rob

[robw]

Found the rev problem, right hand slide sticking only when engine is running.
Any suggestions on cause and rectification
Rob

[robw]

Finally sorted, I put a better spring underneath the cap on the right hand carb, and this has solved the sticky slide. Taking time to ensure that the carbs are synchronised paid dividends as well.
To sum up
300 main jets
25 pilot jets
Air screws 1 thread out
Needle jet- 5 groove from top

No doubt it will need tweaking as it runs in
Cheers everyone for your help
Rob

[steeley]

nice to hear you have got it sorted rob.

[1966baz]

Well done mate - good result.Usually takes abit of patience but you've got there. Cheers Nick.