Ordered smartcarbs

[lost1750GTV]

"Leaner on top" - it is reminiscent of the stock carbs when the main jets were too small, so ..
Yeah, no side panels so the airflow over the carb could be creating negative pressure. I do have the extensions used to adapt the k&n, but figured any/ some effect would still be there. The wilson set up is pretty heavy anyway, and pods with one hose stamp per are simpler for removal.

[Mike]

I own a set of Smart SC Carbs on my RZ500. Now, it has been a couple of years since I have been on this site, but I was searching for other RZ500 owners using Smart SC2 carbs. My Smart Carbs arrived back in Feb 23 and I initially tried to tune them and got sidelined with other things I needed to do on the bike. I recently started tuning them again and here are my thoughts. I did solve the choke issue and I found a filter replacement for the Wilson Performance filters I had on the bike they are way lighter and get the job done. Now to the tuning. I had a hard time starting the bike and apparently, they flood the cylinders quite a bit and yes, I have that issue with the front left carb overflowing out of the bowl. I’ve also been flirting with BH8S plugs, but I ended up burning one (a little too hot), So I’m going back to the B9HS plugs. I am also really concerned with the whole flooding issue because you literally have to pull the carbs & drain before you get the bike running again. Now, why did I go down to the B8HS? I did this because the bike would not fire up using the B9Hs plugs, but also my bike came premix only & motor is nowhere near stock to include larger RZ350 intakes welded to RZ500 cylinders. I am also using RZ350 Mossbarger 8-petal carbon fiber reeds. There is very little stock on this motor too even include the cranks (they are Falicon billet cranks), so I really do not have a jetting baseline to start with, though the folks at Smart Carb have been helpful. I previously had the 34s, which I never got running right, but I did get the 28s working somewhat, so what was I thinking spending $2500 on the Smart Carbs? My RZ has been a journey since I first bought it back in 2006 in mothballs (literally), it was a roller with a motor, no wiring in primer gray. So, the Smart Carbs just seemed like a logical step. That said, I am presently working on the left side throttle cables as they appear to be a bit too long (I got them from Bill Wilson for my 28s & they work great with those carbs), but I am pretty sure I can work this issue out. The lower pipes have a light drip where they mount at the cylinder, but the bike only runs on the choke, so I plan to richin the carbs 5 or 10 clicks and hopefully that will get me running off the choke. But, one good thing is tuning the carbs with a single clicker adjuster. I will work through this and keep all informed because I believe these carbs can be sorted and I do not mind sharing information, so just let me know if you have any questions.

[lost1750GTV]

You've tried mikuni 28 & 34's before these SC's?
And burned a plug?

Regarding the float drain screws, if mikuni makes them as a bolt instead of screw that would solve the clearance problem - I haven't looked into this yet.

I have installed pod filters but haven't had a chance to get back to tuning with the richer (on top) rods yet.

[Mike]

I did try the 28s & 34s, but I burnt the plug with the Smart Carbs on the lower right cylinder using NGK BH8S plugs, which was weird since I've used these plug with no problem with the Keihin 28s. I too haven't looked into the Mikuni drain bolt, I probably need to call Cory at Smart Carb to find out if they know anything about that leaky front lower carb. I too came up with a pod filter solution. Here are a couple of photos of what I came up with for air filters and the black rubber ring is basically a dusk cover when the bike is not being used to keep the elements out.

[lost1750GTV]

I have the not so attractive pk92.

[Mike]

I had those filters, but the above setup is way lighter and I think the entire setup cost just a hare over $50.00.

[Mike]

Quick update, I had said one of the B8HS spark plugs on the lower cylinders was burnt, what I failed to mention was it was the lower left cylinder (same Smart Carb that floods). I will reach out to the folks at Smart Carb, but I am now wondering why all four carbs have the same jetting specs because the upper cylinders run hotter than the lowers on these bikes (I ran 300 mains on the lowers & 310 mains on the uppers with the Keihin carbs). To compound this, I am using Mossbarger 8-petal reeds, which I have had great success with on my AHRMA national race bikes, but Mossbarger reeds run rich, so couple all that with the larger RZ350 intakes tells me I need to lean out the mixture, but when the bike is running and I open the throttle it bogs (like it is starving for fuel). The Smart Carbs were set at 90 clicks when I bought them, so I am thinking I should be running 100 clicks on the lower carbs and 110 clicks on the upper carbs (again, I’ll first clear this with the folks at Smart Carb). But given that Mossbarger reeds run rich, you’d think I should lean the carbs, but remember, I get a bog when I open the throttle, so I’m going to richin them first. Jetting has always been one of those things that you can read it one way and it can often be another…I’m also planning on doing a compression test (maybe tomorrow), but just looking inside the lower cylinders, outside of the slight burn on the right lower left head, the pistons have zero carbon build up on top of them and the cylinder walls show no signs of wear, so that’s good…more to come.

[lost1750GTV]

There are(i think) 3 rz's with them now, each built different, so they have a starting point but not a spec.

[Smoker]

Mike- you have some very interesting mods!

I can see awesome safety-wired brembo calipers in the pic you posted.

Please share, brother. Start a thread. Your stuff is too cool to keep quiet.

[Mike]

Smoker, I will share, because I've noticed a lot of cool RZ's online, but not many people willing to share what they did or their experiences...I am just the opposite, because there were limited numbers of these bikes ever even made, so sharing & learning from others only benefits us all in the end.

And lost1759GTV, I think you are right about the three & that guy Mike out in southern, CA seems to have them figured out or at least that's the impression I get online from the story they ran about his bike, but other than that story online, I've not seen his bike or any other details about it. But I'll certainly continue to share my story with them!

[lost1750GTV]

I do believe the article was done with it starting, but not ridden, and carbs not dialed in. That (championship) bike was built in CA for a fellow in KS if i recall.
I think yours has BST & ohlin etc. Very nice bike.
I briefly lurked on FB and they had both popped up in that time.
Last fall I switched to EF24 metering rods as I thought the as delivered ones were too lean on top, but have not done any tuning since so cant say if they are right.

[lost1750GTV]

Mike, I found my notes from last year - I'm at about 120 clicks and this was pretty good for low speed running .
So you might find 100/110 still rich - I check my plugs after each adjustment. After you get the low speed/ clicks sorted, then you move onto high speed/metering rod, which are more like changing main jets (but without carb removal and gas spillage).

[Smoker]

that guy Mike out in southern, CA seems to have them figured out or at least that's the impression I get online from the story they ran about his bike

I didn't see the story about this bike. If it is someone in SoCal (where I am), maybe I know him, or could make contact.

[Smoker]

That (championship) bike was built in CA for a fellow in KS if i recall.

Just a couple of weeks ago, I was at Wicked and I asked Roger if he's built any RZ500 engines. He told me that he did the top end on an engine, and the bottom was done by Bill Wilson. I didn't ask details... but I could.

[Mike]

Lost1759GTV,
Thanks for the jetting specs and you are probably right about going to 120 clicks because there was an awful lot of fuel in the carb inlet manifolds & cylinders, but I'm also going to reach out to the folks at Smart Carb because as I stated, I don't understand why the upper and lowers are both tuned at the same clicker setting because the upper cylinders run hotter. More to come.

Smoker,

Here's the link to that article about the guy in southern, CA with the RZV500 using Smart Carbs. Nice bike and interesting article but not a lot about those carbs is really mentioned. https://www.bikeexif.com/yamaha-rzv500r-restomod.