97 Fatboy EVO intake manifold leaks ive replaced the seals a few times but the problem quickly comes back. seems like a common problem and not hard to see why with the design relying on the plastic body of the cleaner as the only means of support on an engine that can rattle your fillings loose. I just wanted to explore other options before replacing a manifold with another one that will do the same thing in time. I would like to keep the stock cy carb. Anyone know of any other manifolds or methods to achieve a more secure way of joining the carb to the intake manifold.? I mean, I suppose you could use some type Fernco or no hub clamp but that might be a little too close to breaking the unspoken duct tape rule..same family

 

You didn't mention how you installed it so I'll hit some pointers that you may have done but just in case. To ease installation I install the manifold first with new seals but I don't tighten it. Then install the throttle cables to the carb and then the carb to the manifold. Install the air cleaner backing plate completely. This puts everything in alignment. Now start tightening the right side flange screws until you feel resistance. Go to the left side and do the same. Take a look at the gap between the flanges and the lip on the manifold. As you tighten the flange screws a little at a time try to keep this gap equal until your between 95- 150 inch pounds. With everything aligned before you tighten the flanges it should keep it from leaking. If you're using an aftermarket air cleaner then find your original backing plate and use it for alignment then install the aftermarket one and shim it to fit properly if needed. If you're doing it this way and still leaking I would ask where are you getting your carb seal. Some aftermarket ones are different thicknesses for some reason. It should be a pretty snug fit requiring lubrication.

 

If I may add a couple things... some do, but I don't use grease on the o-rings. Instead use Vaseline. Modern grease will get not hot enough to melt off / seal. Petroleum jelly will. Use grease on the inside of the carb grommet though.

And the OEM grommets do seem a bit thicker and withstand more carb removals before replacement than aftermarket.

I can't find my photos but inspect your intake carefully on the head spigots. If it's been off and cleaned (sanded) too many times, the ends of the outlets will get rounded off near the ends and will also develop a ripple of sorts. You almost have to "feel" the ripple but holding a straight edge on the seal surface of the outlets will show the rounding off.

If the carb has been mis-aligned for too long, the bung will get wallowed out of round and anything more than about .010 out of round will cause problems.

V-Twin makes a reproduction intake and they are ok. You can also get a Screamin' Eagle replacement that will accept either a 40/ 42 or 44/45mm carb. It uses different grommets for the 40/42 and 44/45. Do yourself self a favor if you go that way and order an extra carb grommet because dealers do not stock them. Otherwise, it comes with everything except the flanges. Intake part # 29635-99 Replacement grommet for 40/42 carb part # 27642-00 (brown)

 

We didn't answer your main question - options to keep the CV...

If you could find the "Y" for the pre- '90 Evo (and they're getting hard to find and expensive) and use the rubber compliance fittings between the heads and "Y" then buy the adapter that bolts to that "Y" that converts it to the CV or Mikuni which are the same, all that would eliminate the o-ring / flange arrangement. That eliminates the o-ring/flanges but adds 3 more places they can leak.

Or, you could buy a manifold for the S&S carb and bolt the adapter to that, which is basically what you have plus one gasket.

Or, find a Ram Jett manifold that bolts directly to the heads and you'd still need the adapter mentioned above. Other than those 3 options, you're stuck with the stock type arrangement.

And a backing plate that has been run out of alignment will warp over time as well, causing carb/manifold seal issues. If it were me and constantly had intake problems, I'd replace the manifold with new, ensure the flanges are not warped, replace the backing plate (if stock) and follow tootal's instructions to the letter, taking your time being patient, it should work for many years without issues.

 

Sorry, I wasnt very clear with the deets but the manifold was leaking at the carb seal. Its been pretty loose fitting since i bought the bike. Havn't replaced the manifold yet but im ordering one after reading this and others on the forum. Its pretty clear this one will never seal properly. couple weeks ago when starting it up warm, The carb coughed and it damn near blew the air cleaner off and i could hear it sucking air from that seal over the engine. it blew the carb off the manifold. lol Also this would most certainly account for the CV carb being unresponsive to mixture adjustments. I was about to give up on it thinking it just wasnt capable of throwing enough fuel out having tried re jetting and all that. Never had a chance the way that manifold was sucking air. Prob could've tuned a garden hose w/ a bucket of gas better. So Ive got the bike stripped down somewhat, I'm putting 16" apes on as well as a couple smaller mods in addition to replacing the manifold. I will update when its all done. thanks for your help.

 

Make should you have the correct size manifold to carb seal.

 

Ok, that clarifies things a lot.

Do order a brand new one! Don't rely on a used one, as 90% of them will be bad or deficient (trust me and don't ask how I know - lol) and the new ones, even the Screamin Eagle I mentioned earlier aren't that much more $$ over unknown used ones. And again, the OEM grommets do seem a tick thicker and hold up better/longer.

Good luck