V4 Series Carburetor Restoration

The pictures below should tell the story better than me tooting my own horn. You can do that once you've got your bike running again but I prefer to let my reputation speak for me. I ship carbs all over the world and the demand is steady even in this economy, for which I'm eternally thankful. Naturally this means that I have a healthy backlog. Expect about 8-10 weeks from the time they get here to have them on the way back to you.


The price for the service is $735.00 plus return shipping. To ge the process started, download and print the Service Request PDF on the left.


As you scroll through the gallery you'll see some before and after shots. There are no tricks here--the ones in the "after" photos are the same carburetors as in the "before" shots.


However, making them pretty has absolutely nothing to do with how they'll work so I pay even more attention to the insides.


Every jet comes out and every orifice gets cleared. Some of the internal passageways are connected to each other so we make double and triple sure that those critical areas are completely clean and clear.


A lot of folks aren't aware that the forward and rear carburetors are different even though the parts look identical at a glance. In fact the only things that the individual carbs in a given set always share are the slow jets, the air/fuel mixture (pilot) needles, choke plungers, and the slide/diaphragm assemblies. Depending on your model, the forward and rear carbs may have different needles, main jets, emulsion tubes, and slide springs. If they get mixed up by a well-meaning novice the bike won't run properly.


It's a real bear to synch V4 carbs on-bike so I spend extra time setting them up so you won't have to. That being said there are the occasional times when you'll have to final synch but it's extremely rare and is generally the result of one cylinder having a previously undiscovered problem.


I prefer an informed customer so if you're an old hand you may not benefit from having this repeated but there are a couple of things we'll want to address while you've got the carbs off.


First and most important is to check your compression. V4's are very robust engines and will run fine all the way down to 100 psi even though the spec is 170. What we're on the lookout for is one cylinder that's significantly lower than the others. If I had a motto it would be something along the lines of "If your compression is good, the rest is just details. If it's not, you're dead in the water." I'm happy to take your money but let's make sure my carbs solve your problem instead of reveal others.


So, get a compression tester and follow the directions. If you find one cylinder that's more than a few PSI different from the others we'll need to sort it out or else you'll be in the same pickle.


We also want to make sure that the air cleaner is in good shape. I've seen instances where a guy thought his engine was in trouble due to blowing black smoke and having trouble starting when all that was wrong was a dirty air cleaner. Sometimes it's the little things that bring a bike to its knees and this is a simple item to remove from the list of variables that might be giving you grief.


Another nagging thing about the V4 engine, and one that dovetails with compression-related issues, is an inherent weakness in the cams, which under hard riding suffer from insufficient oiling. For some reason Honda elected to route oil from the low pressure side of the pump to the heads and high pressure to the transmission instead of the other way around. I also believe that it's partly due the owner letting the oil level get low, but whatever the underlying cause over time they'll erode and the valve clearances will proportionally shrink, sometimes to the point where compression is affected. If you've got a lot of clicking noises coming out of the top end, chances are that at the least the valves are out of adjustment.


It's surprisingly easy to adjust the valves and even replace a bad cam if need be so don't despair if you see a cam lobe that's torn up. Once repaired it's unlikely to recur and I can walk you through the process.


We should also inspect the water pump. Some models have a metal impeller instead of hard plastic and I've seen them erode down to mere nubs. This is all the more important to have a look at if your engine has been tending toward the hot range.


You already had to pull a lot of the cooling system parts off to get at the carbs so go ahead and drain the system all the way and have a look at the pump innards. While you're at it, use your garden hose to flush water through the tubes that feed coolant into the heads. This will clear out any crud that may have accumulated in the water jacket spaces around the cylinders. A small blockage in there can cause a hot spot on a cylinder wall and lead to trouble if left unattended to.


If you see telltale evidence that the water tubes are weeping, you needn't buy expensive seals. A pair of 1/2 inch inside diameter x 3/32 thickness o-rings take the place of each seal, which you can get at your local hardware store. You may find that the pipes are as good as glued into place with corrosion so hit them the night before with some PB blaster or marvel mystery oil and it'll go much easier. Emery cloth or 220 grit wet/dry wrapped around your finger will clean the chalky residue out of the bosses in the heads. A dab of petroleum jelly and you're ready to go.


Once you've got the valves, cams, and cooling system checked out, a set of freshly redone carbs will bring your bike back to its old glory.

Here's Where You'll Find Us:


1346 The Alameda Suite 7-80

San Jose CA 95126

Phone: 408-921-1735


Email: Jack@oldschoolcarbs.com

SERVICE REQUEST Click the PDF logo to the left or the link below to open a blank form to print, fill out, and include with your carbs.
OSC Service Request.pdf
Adobe Acrobat document [66.0 KB]

If there's anything you need for your CBX, Bill is the one to call.

Digital Pizza is where you'll find Pete Rose's genius at work.


Click on the logo for a 100-Point restoration not only of a CBX but other Honda Inline 4's.


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