Carb swap

This is really part of my earlier post another carb question, but I don't seem to be getting an answer there so I'm making a new post instead, hopefully with better results.

In the intrest of trying to solve my popping issue, I'd like to know if I can swap carbs from my '90 FLTCU to my '05 FLHTC? The FLTCU runs perfectly and since I can find no vacume leaks on the FLHTC, I'd like to try a known good carb to help pinpoint the problem.

Aloha...Mike

Yes you can...

sir rat, how are you trying to find the intake leak? spraying stuff around manifold or pressure testing? pressure testing is the best way i've found to check for leaks.

what kind of exhaust are running, lack of a good baffle will sometimes cause a poppong when decelerating, Carb cleaner works very well well for checking for air leaks and doesn't leave a mess.
Have you tweaked the carb any? Not everything works on every bike, don't get frustrated CV's are the best carb out there, I run one on my stroker 103.

I find using a propane torch(unlit) to be the cleanest and easiest way to find intake leaks...

Exhaust leaks will also give you decel popping

hope this pic works. remove the carb and use the block off plate. with the intake valves closed put in about 10lbs of continuase pressure and brush on some dish soap around manifold, heck check plugs while your at it.. it will find the smallest of leaks. spray stuff is good to a point but you'll find teeny leaks with this.
most of this stuff you mite have sitting around to make one.

I can see that work on a flange style manifold,but you'd need a big rubber stopper for spigot style manifold like the CV carb uses and zip ties to secure it,or have you used it on spigot style manifolds too??

lucifer, that plate is for my linkert manifold(took wrong pic) i have a plate with 2 threaded holes for a cv manifold.
heres that cv adapter for the retrofit to an sns o-ring manifold.
Harley CV Carb Flange Shovelhead Sportster | eBay

Yep seen them for mounting CV's on pre 1990 butterfly carb 2 bolt manifolds and S&S...no bolts to mount a CV carb on a CV manifold 1990-up...here's a couple of pics....CV's are push on with a sealing ring...

Thanks lucifer. i got my head so wrapped around the carb on my bench i didnt notice the 2005 date sir rat had mentioned.

could very easily be the rubber boot carb to manifold is leaking, apply a little light grease before installing the carb in the manifold,

Sorry guys I should have posted more info...I'm running an (per the dealer) "Open Element Air Cleaner". With stock pipes running into Rush muflers.

I had these same mufflers on my '90 FLTCU using rush true dual pipes, with a bone stock carb/air cleaner and that bike ran perfectly.

I used breakclean to check for leaks. I get that the pressure tester is the best way, however for the amount of time and the labor it would take for me to make one, I would think it might be easier and less costly to just go ahead and try a known good carb (such as the one off my '90 FLTCU) The pevious owner had already screwed around with the carb on the '05 FLHTC (knocked out the plug and re-jetted) right now the carb has a .210 main jet and a .45 slow jet. The bike pops on the upshift between gears and on deceleration. Idle is a little high, I can turn it down but then I have to run it for a half hour to get it totally warmed up or else it dies at the stops unlesss I keep feeding it. When it does warm up to where it will idle on its own it surgess a little. Like 1000-1100 rpm for about 10-15 seconds then drops to 850-900 rpms for 3-5 seconds then back up to the higher rpms. The bike only has 9000 miles on it now, (Yes I know thats no guaranty its not the valves) but for now I don't think (AND I DON'T WANT TO THINK) it could be something like the valves/valve guides. The Vance/Hines mufflers that came with the bike were pretty quiet and I certainly heard no exhaust leaks then and I still don't hear any now. Not knowing exactly what the previous owner did to the carb is also a major factor in why I would like to just try another carb. Anybody ever deal with these folks on Ebay, KILLER M/C PRODUCTS? Their carbs have been tricked out and totally re-worked with, re-jetting, polished slides and flow tested ect ect. Doesen't sound like to bad a deal for under $300, I might even go that route rather than yank the carb off my perfectly good running 90 FLTCU.

I have a propane torch around here somewhere and will give it a try first, thanks for the help guys...I'll post up as to what the outcome is.

Aloha....Mike

Sir rat...did you take the carb off and clean it....could be as simple as a loose pilot jet or partially plugged pilot...all the dealer did when they rejetted it seems was put in a larger main jet,because a 45 pilot is what the bike had in it from the factory...

For what it's worth.
The 45 is to small for you altitude and an after market air cleaner, the 210 is to big for the same reason.
As long as no one has jacked with the slide there is no reason to assume the carb is messed up. As Lucifer stated try cleaning rejetting to a 46 or a 48 and a 190 main. The stock needle should be in the middle groove. Be care full of the rubber boot around the top of the slide.
Brake cleaner is not as volatile as carb cleaner and doesn't work as well when checking for air leaks. Before I spent $300.00 for the same carb, I'd experiment with jetting and maybe even put the stock air cleaner system back on it. Just to check it out.
Did it pop when the other pipes where on it? How many miles on the bike?
You can try the carb off the other bike but you need to know what jets are in it first.
Lastly read all you can about how to tune these carbs, they are very basic and really they are easy to work on. There is a ton of information out there on these carbs.

I lucked out and got a remanufactured CV carb on EBAY for $162 including shipping. The slide has been polished. The jets are 45 and 190 main. The idle mixture screw plug was in place. I knocked the plug out and installed the EZ just screw, the Needle & 46 slow jet from the CVP Tuners Kit and left the 190 main. If this rain ever stops I'll install the new carb and use a propane tourch to check for vacume leaks. At least this way I'm starting with a carb that I have some knowledge of its history. If the rain doesn't stop soon I may have to start building an ark instead. How many inches in a Cubit???

In the way, way back good old days, a cubit was the distance between the tips of the fingers and the elbow. About 18". Check the slide and be sure the vacuum hole is no larger than 7/64". Some people drill them out to an 1/8" or even larger and that creates problems as well.

OK the rain has finally stopped and I was able to swap the carbs. I did not remove the gas tank, only took out the bolts and wedged the tank up out of the way to gain better access. I got everything hooked back up and adjusted the cables. I opened the petcock waited a few minutes and tried to start the bike. Nothing.....no pop, no backfire....nothing. Pulled the fuel line back off and got a very, very small trickle of gas and then nothing. I got better than half a tank but no matter where I position the petcock I can't seem to get any flow at all. I guess that vacum line to the pet **** has something to do with that? I have not dropped the tank back down yet, wanted to see how it runs first. Ran out of daylight, will try to finish up tomorrow. I will find a way to prime the carb first or else maybe just get some ether spray. Hopefully thats all I need to do to get the bike started so I can finish up.

I took a good look at the carb that came off. The slide had not only been drilled, it looked like it had been filed, I guess the monkey doing the work was trying to make the slide move easier or something like that.

Aloha...Mike

If the vacuum line is not on the petcock and carb,gas won't flow....the vacuum operated petcocks will only flow when the engine is running and pulling vacuum...the diaphragm in the petcock is another place that can cause a no flow condition...so if the vacuum line is hooked up and no cracks or breaks in it,the problem is the petcock....