Hi all. I have a slight issue. my VFR carbs have bitten the dust with all the threads snapping. I have now bought some RVF carbs and fitted them. The issue here is, I cant get the bloody things to run right. I have had them all apart and cleaned them out. They seem balanced but, the cylinders 2 and 3 have bugger all suction. Any ideas how I can balance them correctly. I do have some gauges but no idea how to go about it with the RVF carbs.

Thanks.

Ive never bothered with vacuum gauges i just use a drill bit to balance them but each carb has a point to attach the pipes to just like the 30 although in a different place i think, haynes manual should tell you where they are.

Whats jets etc you running? stupid question but best to check, you havent swapped the jets etc over from the VFR carbs to the RVF ones have you?

Tazzer1993 wrote:Hi all. I have a slight issue. my VFR carbs have bitten the dust with all the threads snapping. I have now bought some RVF carbs and fitted them. The issue here is, I cant get the bloody things to run right. I have had them all apart and cleaned them out. They seem balanced but, the cylinders 2 and 3 have bugger all suction. Any ideas how I can balance them correctly. I do have some gauges but no idea how to go about it with the RVF carbs.

Thanks.

sounds like you have a major issue here, ive never seen any threads snapping on carbs before unless they were attacked with a hammer? what is the proper story?

What do you mean they "seem" balanced.. is this based on a set of connected vaccum gagues?

How do you know cylinders 2 and 3 have no suction?

The carbs balance exactly the same as NC30 carbs you connect the gauges and adjust the 3 balancign screws with the engine warmed up and slightly higher idle.

What settings did you set the RVF carbs upto they run different to nc30 carb settings, float heights, pilot screws etc.

Drunkn Munky wrote:Ive never bothered with vacuum gauges i just use a drill bit to balance them

I dislike the drillbit method, it is ok when rebuilinng a completely stripped set of carbs to get the ballpark figure right (althoguh I can do this by eye) but there are two things, its static balance and dosent take into account vaccum differences from the cylidners and ive seen on some carbs after mounting to the rubbers, although it shouldnt happen the linkages seem to go a little out of synch.

Set of morgan carbtunes and right angle screwdriver and no trouble on any bike, mine have been all over the world and paid for themsevles many times over

Right, the carbs were a straight swap from one machine to another. All the butterflies are practically dead on the same. That's what I meant by seem balanced.
The threads snapping must have occurred when it was stolen. When I got it back it ran like crap. Once I had taken it all apart I noticed that the carbs wobbled about from each other.
I had the engine running and put my hand over the trumpets to gauge if all 4 were doing as they should. 2 and 3 didn't suck at all even when icreasing the revs. Obviously it doesn't rev very well. Just splutters a lot and bogs down at around 6k and will not go any higher.
The carbs came from a stored RVF but, the fuel was never drained. All the jets and screws have been cleaned out and put back exactly where they were. Despite this, they just won't work. The float on 3 was a bit stiff when I took it apart and didn't seem all that much better once it was cleaned but, that still doesn't explain why 2 doesn't do it's job.
There are no air or fuel leaks anywhere and the inlet rubbers are brand new.
New jets perhaps?

You put your hands over the trumpets with the throttle closed? No "suction" really sounds more like an engine problem. The piston lowering in the cylinder is what causes the suction.

Buy a haynes manual or download a work shop manual on here. Also, get a proper guage set to sync the carbs (morgan carbtune and angle driver is perfect to start with). Dismantle the carbs slowly and organize per carb. Loosen all float bowls and all inner jets and even better at this stage is to ultrasonic clean the body and everything else as loose parts. Start from scratch will help to avoid incorrect readings or assumptions, and set to a starting point with new seals. Correct set float height is crucial to get it all started. Of course clean filter and clean/new plugs help even better. Forgot to mention that the carbs fitting back on the engine will be easier with new carb rubbers. Any air leak after fitting carbs has to be avoided (double check to be sure that the carb banks sit correct).

I have discovered the issue and I now feel like quite the numpty. Put simply, the fuel lines were blocked. I didn't even think to check them. Now runs sweet as a nut. Certainly won't be making that mistake again.

On a separate note, is there any way to increase the power by fiddling around with the carb insides? I am well aware that I will be needing to up-jet it when I put the new exhaust on. How much bigger will I have to go? Will be putting a full stainless system with a straight through Yamamoto can.

as above, its all in the carb guide.

you wont really get anymore power out them no matter what you do unless you are willing to spend serious money on pistons and rods and things.

they were pretty well strung out from the factory.

generally the maximum youll need to go is the next size up in jets, most of the aftermarket systems make use of stock jetting.

Tazzer1993 wrote:I have discovered the issue and I now feel like quite the numpty. Put simply, the fuel lines were blocked. I didn't even think to check them. Now runs sweet as a nut. Certainly won't be making that mistake again.

On a separate note, is there any way to increase the power by fiddling around with the carb insides? I am well aware that I will be needing to up-jet it when I put the new exhaust on. How much bigger will I have to go? Will be putting a full stainless system with a straight through Yamamoto can.

There is no real guide line for this. And do you talk about an upgrade or maybe a downgrade of exhaust systems, from what current system to that system and exhaust?

micpec wrote:

Tazzer1993 wrote:I have discovered the issue and I now feel like quite the numpty. Put simply, the fuel lines were blocked. I didn't even think to check them. Now runs sweet as a nut. Certainly won't be making that mistake again.

On a separate note, is there any way to increase the power by fiddling around with the carb insides? I am well aware that I will be needing to up-jet it when I put the new exhaust on. How much bigger will I have to go? Will be putting a full stainless system with a straight through Yamamoto can.

There is no real guide line for this. And do you talk about an upgrade or maybe a downgrade of exhaust systems, from what current system to that system and exhaust?

It would be an upgrade. According to the specifications, it can give up to 5% power increase depending on how you accommodate it. The current exhaust system is a bit shot. It has many, many holes in it and has been welded together from many different bits of exhaust. I shall be honest, it's an utter mess. The best I can do while I have it before the new system arrives is to just use lots of gungum, tin cans and jubilee clips. As far as exhausts go, this one has pretty much had it.