Jetting

[fatboy]

Hi there,looking for a little help on jetting for my rd350lc.Completely rebuilt, brand new mikuni vm26-8074 carbs.micron expansion chamber,boyesen dual stage reed valves,boost bottle,6mm reed spacers,y-pipe with k and n filter.Engine has not been ported or modded internally.Im 3300 feet above sea level here in Canada.I put 27.5 pilot jets in and 250 mains,needle clip middle.Bogs down right from a stand still trying to pull away and will not rev hard.Any advise from where I should start jetting would be great.

[nokturnal]

Its an 81-82?

27.5 is a large pilot for an 81/2, if they are the standard carbs. If it was my bike I would try the standard pilot and air screw settings.

That main jet is way too small for a y boot... last time I ran one (and stopped dt horrific gas mileage) I believe I was getting close to 400... was a long time ago, so hard to say. You will melt a piston at 250 though.

[markhoopy]

Have you seen the information on this page for standard setup?

rdlccrazy.proboards.com/thread/7098/jetting-carbs

[bare]

Boysen trap door reeds..boost bottle... Reed spacers. Someone has drunk the Koolaid :-)
Remove and bin those bits.. they detract rather than help.

[4l04ever]

The Y-pipe with K&N filter can greatly affect jetting. Standard Airbox is preferred and you know what jetting to at least get started from. Potentially you would need to upjet considerably to allow for the increase in airflow.

[ozzysbikes]

Mar 15, 2020 3:20:34 GMT 1 bare said:

Boysen trap door reeds..boost bottle... Reed spacers. Someone has drunk the Koolaid :-)
Remove and bin those bits.. they detract rather than help.

I never got the Boyesen dual stage reeds and they never improved anything I have owned, we used to use Harpowa reeds in proddy racing one big petal with the centre bridge removed, Boyesen dual stage reeds are supposed to open the small petal first but I have no idea why just opening the big petal by a small amount is any worse than opening the small petal !! Boost bottle tried one on the YPVS, if anything it ran worse, reed spacers I would say are effective but only for a certain rev range my air cooled 350 does seem to be stronger at the bottom end with the spacers fitted (still runs nice either way) and purely from a visual the standard reed block without the spacers does mask the boost port, I don't think the spacers give any more power just help torque slightly, that is how it feels out on the road.