Yes, some Walbros come with the choke plate some don't. If you have a V-stack with choke you can run the V without the thin choke plate, or you can remove the choke plate in the carb and run the V choke arm, I have both. If you stock carb and v stack are 15mm the 16mm choke plate will hit the edge, need to make the hole bigger. I run a 19mm V-stack w/ choke arm on a 603 with the choke plate removed.
Sounds like the problem, happened to me already. The manifold, that's the problem. The make alum manifolds, got mine for $16 w S/H, the plastic ones suck. The stock manifold and even the alum you need to fill in the lower part of the pulse channel so the 16mm don't have a intake manf leak. Before you ask the tube goes to the boost bottle.
Got to be for a 49cc piston port engine, cateye, X7, scooter, they all use the same 15mm pumper copy carb and manifold. I have 9 bikes, so I order alot. scooterpartsRus online is where i got mine. PB intake manifold $12.99 and $2.99 S/H, it comes w/ the black spacer ready except for your boost fitting,lol.
I fill parts of the channel w/ yamabond and cut a gasket that covers the the channel on the bottom side, and just leave alittle at the top to connect w/ the pulse hole in the carb. I have modded two other engine manifolds to work, but it's alot of machining and modding.
That manifold is only 15mm, the rear carb hole is 15.88mm, .034" bigger. You can round the front lip or taper it out to 15.88mm on the main bore of the intake manifold to match the carb, or bore the manifold all the way thru to 16mm. I have a dremel elect. rotory tool and a drill press that I use for stuff like that. The 4 reed manifold was 15mm I needed 19mm, so, I marked it with a felt pin & I hogged it out w/ a hand drill & 1/2" rotory file.
This is a 19mm Walbro HDA 48D on a 4 reed intake box, mount to one of my twin drag bike engines.
You may also need to get the proper velocity stack. If the choke is a separate unit your good to go (just don't use it). If the velocity stack has a built in choke you will need to either a) get a stack without one or b) remove the butterfly "disk" from the choke arm in the carburetor.
i seem to have the right v-stack. installed without the choke that came with it.the carbs chokes to open fully no problems and close no problem. The other plate the same. the manifold on there now is temporary till i receive the metal one with new gaskets.
Dude, your set then,lol. I have 16mm I took the choke out on some and I left it in on others. If it ain't broke don't fix it, you will have enough stuff break to keep you busy,lol. Hugh at SD Scooters gave me a great deal on this Walbro 19mm HDA 223 purge carb and I modded a GS 40 billet intake manifold to fit them together haven't run it yet, it looks Sick.
For $60 from Boosted306, Sam, get a ported 49cc piston port head, I have one on my scooter engine, comes w/ a new set of rings. That and an 813 walbro and jet pro exhaust and it screams Now,lol. To make it faster leave the base gasket off and a thin layer of yamabond and drop the cylinder on, put the bolts finger tight , come back the next day and tighten.
If your serious, I have his e-mail address. He has jobs and does this on the side so don't waste his time. Your not going to get a better deal, he takes the stock Hd/Cyld and mods the hell out of it, even comes w/ a new set of rings for the new cyld, $60 shipped.
I have a few of his Cag reed port 49cc Third Stage Billet Head Kits, sent him my engine and carb, and $115 he put his kit on and he taper swirls & line bores the carb from a 12mm to 17/14mm rejets its starts it on his enginestand and ships it back too you, ready to Rock 7 Roll.