Jetting help please 1GW ypvs

[cjr]

Hi folks, I've got RD 125 LC French import. Bike did have flat slide carb. That was 110 MJ, highest needle pos. It wouldn't revv past 85000 and smoked like hell.

Now fitted eBay VM 24 and worked better, revving round to 9000. Carb arrived with 110 MJ and I set needle to highest position , top notch, not lowest.. Read alot about 10a and 12a engine's, sorry if im being thick, but the numbers say 1 G W. Perhaps this French import, working ypvs, is different? I've fitted 155 MJ, lifted needle to middle position and problems starting.fyi  Running premix 1\30. Even with the old carb it started first or second kick.

Have fitted new foam filter, original air box, set valve to align with dot. Reeds are polini and a little warped. So will swap them round. In the old days I used to fit hytec reeds, but they all seem to be carbon now? Exhaust is black with silver can. Looks like it's had open heart surgery! About to buy allspeed. Air box rubber is not original, just a peice of tight hose. Air screw set to one and half. Bike feels like it wants to rip, but doesn't. Although it was 1988, im certain my old MK3 non ypvs was much faster. Pulled a tonne no probs.

Any ideas please? Notch higher on needle, MJ back down to 110? Im thinking original air box rubber manifold might benefit.

Advice appreciated please, cheers, Chris

[tony2stroke]

Jul 19, 2020 18:43:52 GMT 1 cjr said:

Hi folks, I've got RD 125 LC French import. Bike did have flat slide carb. That was 110 MJ, highest needle pos. It wouldn't revv past 85000 and smoked like hell.

Now fitted eBay VM 24 and worked better, revving round to 9000. Carb arrived with 110 MJ and I set needle to highest position , top notch, not lowest.. Read alot about 10a and 12a engine's, sorry if im being thick, but the numbers say 1 G W. Perhaps this French import, working ypvs, is different? I've fitted 155 MJ, lifted needle to middle position and problems starting.fyi  Running premix 1\30. Even with the old carb it started first or second kick.

Have fitted new foam filter, original air box, set valve to align with dot. Reeds are polini and a little warped. So will swap them round. In the old days I used to fit hytec reeds, but they all seem to be carbon now? Exhaust is black with silver can. Looks like it's had open heart surgery! About to buy allspeed. Air box rubber is not original, just a peice of tight hose. Air screw set to one and half. Bike feels like it wants to rip, but doesn't. Although it was 1988, im certain my old MK3 non ypvs was much faster. Pulled a tonne no probs.

Any ideas please? Notch higher on needle, MJ back down to 110? Im thinking original air box rubber manifold might benefit.

Advice appreciated please, cheers, Chris

Clip in top notch lowers the needle weakening the mixture, bottom notch lifts the needle making mixture richer, sounds like the flatside was running rich to me, middle position on needle is where they are normally on standard carbs.

Running pre-mix means you need a larger main jet to accommodate the oil going through the jet.

You can still get old style Hytec reeds, Yambits or Wemoto I think still do them, nothing wrong with carbon reeds, used them myself.

If your using standard airbox I would get a gen Yam rubber, Norbo does them in the shop, cheap enough for gen Yam ones £15, here's a link.


www.rdlccrazy.co.uk/html/for%20sale%20page%201.%2080lc125lc%20%20.htm


HTH

[Chris jr]

Thanks for the advice. Will try it this morning and update.

Original set up:
Flat slide carb
110 MJ
Need clip lowest pos
No air filter

Bike started easily, only revved to 8500, smoked like a trooper.

New set up:
eBay VM24
110 MJ
Needle clip highest slot
Air filter foam fitted

Update. Needle clip middle, not starting. Needle clip lowest position, started first kick, and really smokey. Will take it for a spin lunch time. I guess my next steps are:

Fit airbox manifold rubber, will order this morning
Upjet if still won't revv out
Await delivery of Allspeed

Appreciate your assistance. Is the ideal solution fitting mikuni carb?

When this bikes doing what it should, my RS125 DX is getting some attention. Going post office later to register tax and mot exempt.
Thanks again!

[Chris jr]

Thanks for the advice. Will try it this morning and update.

Original set up:
Flat slide carb
110 MJ
Need clip lowest pos
No air filter

Bike started easily, only revved to 8500, smoked like a trooper.

New set up:
eBay VM24
110 MJ
Needle clip highest slot
Air filter foam fitted

Update. Needle clip middle, not starting. Needle clip lowest position, started first kick, and really smokey. Will take it for a spin lunch time. I guess my next steps are:

Fit airbox manifold rubber, will order this morning
Upjet if still won't revv out
Await delivery of Allspeed

Appreciate your assistance. Is the ideal solution fitting mikuni carb?

When this bikes doing what it should, my RS125 DX is getting some attention. Going post office later to register tax and mot exempt.
Thanks again!

[tony2stroke]

Jul 20, 2020 10:31:25 GMT 1 Chris jr said:

Thanks for the advice. Will try it this morning and update.

Original set up:
Flat slide carb
110 MJ
Need clip lowest pos
No air filter

Bike started easily, only revved to 8500, smoked like a trooper.

New set up:
eBay VM24
110 MJ
Needle clip highest slot
Air filter foam fitted

Update. Needle clip middle, not starting. Needle clip lowest position, started first kick, and really smokey. Will take it for a spin lunch time. I guess my next steps are:

Fit airbox manifold rubber, will order this morning
Upjet if still won't revv out
Await delivery of Allspeed

Appreciate your assistance. Is the ideal solution fitting mikuni carb?

When this bikes doing what it should, my RS125 DX is getting some attention. Going post office later to register tax and mot exempt.
Thanks again!

The starter cercuit is pilot jet which then goes to throttle cut away as you open throttle then to needle jet as you open throttle more which then goes to main jet at 3/4 to  full throttle.

Try a bigger pilot jet and put needle clip back in the middle is my advice and see how you go, but also get the manifold rubber.

[tony2stroke]

Think I would go back to the flatslide carb put needle clip in middle and see what happens, though I would use an air filter of some type.

[Chrisjr]

Thanks, I understand.

Starting issues relate mainly to pilot jet, needle after that at middle rev range,main jet top end.

I'll take out pilot later and see if there's a kit out there with main jets. Replace needle clip to middle.
Thanks again!

[Chrisjr]

Hi, needle back in middle pos. Starts first time. Still bogs out high revvs, so removed filter and air box cover, and it revvs better. Given what I now know, more air is trying to balance out the rich intake so trying smaller main jet.

On another note,need to order original indicators, and adjust headlight brackets so fairing is neat and square.looked and struggling to find fairing brackets,got left side so far which is enough to copy a right hand side. Only looks like mild steel so should be easy.

[tony2stroke]

Which carb is this now.

[cjr]

Hi Tony, I've fitted an eBay VM 24 copy. I've realised there's no point trying to apply factory settings to the wrong carb, on the 1GU working ypvs, unrestricted engine. What I really want to know is what carb belongs on this engine?

Some investigations show it should be VM 26ss? Any advice on this greatly appreciated.

Also, does mk 1 exhaust fit MK2? Found an unrestricted MK1 exhaust I might buy.

As always, thankful for the help and guidance. Cheers, Chris

[mellow]

yes it should. MK 3 pipes fit mk 1 and 2

[tony2stroke]

If you have look on your other thread, mellow and I have posted the correct carb there mate, mellow posted the correct jetting for that carb for you, I also posted a link to Fowlers for you to see the correct carb, if you post a couple more times (you need 10) you can then put an add in the wanted section asking for any that are for sale, though I wouldn't hold your breath waiting.

You may be better off trying to get your flatslide to work, almost any carb can be made to work with the correct jetting, personally I would try and get the flatslide jetted correctly to suite your bike, That is if its 26mm or bigger they are good carbs.

By the way, its not the engine that's unrestricted, its the carb and exhaust, the porting is the same on either bike, the MK1 exhaust will fit, though it won't be as good as a YPVS one performance wise as they are tuned to different lengths of pipe, the YPVS will rev higher than the none YPVS and be slightly shorter allowing it to rev higher, you could cut a standard YPVS pipe and remove the restriction, but if you don't know what your doing I wouldn't advise doing that.

You may be better off looking for a tuned expansion chamber that will allow it to rev higher, depends what you want from the bike, a gain higher up the rev range will cause a loss of power lower down and vice versa, its all swing and roundabouts with 2 strokes.