Carburetor swap - replace Amal and Dellorto VHB with Keihin PWK

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models

Thanks to Charlie Mullendore of Antietam Classic Cycle for sending me Mike Tiberio's conversion information via email. In Mike Tiberio's own words and photos.

I have been posting about this on the loop list, but I should really spread the news. I have been looking for a replacement for the old square slide VHBs for a while. I found a Chinese made Keihin carb knockoff modified to replace British Amals. Mating a pair of those with a set of the Guzzi Amal manifolds (yes small valve roundfins came with Amals for a while in 1974 I believe) is possible and practical. Other than buying the manifolds, the carbs, and a pair of off the shelf throttle cables, the whole conversion required no machine work or other special fitting or cutting (other than fuel line).

I have never installed a totally different carbs on a bike and had them work as perfectly as these carbs did tonight on my Eldovert. It all jelled when I got some throttle cables in from MG tonight. I asked the guys at MG to measure the freeplay of their throttle cables, and asked them to send me a pair of whichever ones had the most freeplay. It ended up being their no name throttle to VHB cables. I knew the Keihins ate up more cable than the VHBs so I thought I'd start with these cables. As I was doing some measuring tonight trying to figure out how much I was going to modify the cables, I realized they would work with my Tommaselli 2C throttle and the Keihins as delivered. Then I realized I had everything I needed, and by 8:30 I had them installed. I went to start the bike and it didn't even cough. Oops, I left the spark plug wires off (I removed them to get them out of the way). Once I had spark, choke, the bike started right up and settled into a decent idle. I rode off down the street, and by the time I went 3 blocks, it was idling high, oops I left the chokes on. Chokes off and it idled perfectly, and ran great in my residential neighborhood. Quick to get home, finish buttoning up the tank bolts and put the saddle on, get my jeans on and head out for a top speed run. Bike pulled cleanly to 100, and I ran out of road. I'll have to watch the gas mileage, and do some plug chops to get these carbs any better set up they are that close. I uploaded some pix so you can see the sano install with the Guzzi Amal manifolds.

They have carb mounted chokes, but a cable kit is available, I might spring for that. They take ¹⁄₄ inch fuel line, but since I was set up for filters that take ¹⁄₄ inch line, that issue was no sweat. I was using dual spigot banjos on my VHBs for a crossover, I'll either have to T each line to do the same or use both petcocks. I do have a set of Tonti petcock adapters, so that will give me a reserve back if I don't go for a crossover. The inlets are about 2 inch dia, so I'll probably pick up a pair of UNI filter foam socks to handle the air cleaning chores. There are no clearance issues between the float bowls and the bell housing. In other words, a bolt on perfect fit as long as you have the Amal manifolds. Oh yea did I mention the throttle pull is oh so much lighter.

More later...

The carbs are made by a Brit Bike specialist called JRC Engineering. They are Keihin PWK oval bore (28/30) semi flat slide carbs. They are big with the moto cross crowd. JRC doesn't do retail, and has dealers. I used Specialty Spares (253) 853-1420 (no longer in business). They were $100 a pop plus $15 shipping. The manifolds were made by Moto Guzzi to allow mounting of Amal carbs to Eldos back in the early to mid 70's (either Dellorto couldn't supply enough carbs to Guzzi, or Guzzi didn't pay their bill!?!). No one ever liked the Amals on Guzzis, so the manifolds are easy to find used. While a lighter throttle pull is one reason to convert, I was hoping for more precise metering and adjustability, together with a sense of lets do this because we can.

Dec. 5th, 2011

Still on the bike. All I did to jetting is go one smaller on the idle jet to 35, and lean out the idle mixture screw to 2.25 turns off seated. 37 to 39 MPG with my Convert.

Still occasionally pops, but then so did the VHB's. Bike does have 155,000 miles, so I don't expect perfection. Throttle spring is soooo much lighter. Like FI. I recommend this modification to anyone that has 29 mm or 30 mm VHB carbs.