The FIRST of my eBay purchased H1 carburetor sets has arrived and, as described, is in poor condition. I'll document the "As Received" condition in pictures below. This set was purchased for $60 solely for parts that are missing on the second set of H1's that are arriving soon. A new heat shield alone would exceed the expense. Parts that I hope to refurbish include the heat shield, air filters, some metal tubing and minor linkage bits.
The first step today is to drop the entire setup into a tub of Evaporust to see what can be cleaned up before I begin to dismantle the manifold, heat shield and carb bodies. Below is an excerpt from the AH Experience Forum port "H1 SU Carbs" by Mike P:
"The BE's H1 carbs were among the last of the 'H' carb series. The 'H' series had a lot of parts, meaning more possible failure points. The later 'HS' series simplified the jet/jet bearing assembly, making carb adjustment and balancing much easier.
Brooklands Books publishes 'SU Carburetters Tuning Tips and Techniques.' This compact manual provides good information, beginning in Chapter 7 on dismantling, reassembly, and tuning. Remember, this is an 'H' type, as this (and all other manuals) jump around a bit, so follow the text about H-type tuning.
Other important tips: The H type is adjusted mostly through the jet adjusting nut. Up and down (left and right turns) leans or enriches the fuel flow. The jet adjusting nut is a Whitworth size, so it doesn't have an ASE or metric equivalent. All suppliers will offer a single adjustment wrench - consider getting one.
The carburetor air flow meter sold through the various suppliers is great for balancing carbs, but is too big for the H1. The carburetor synchronizer tool can work, but is designed for later carbs. Your H1 has a 1 1/8th inch diameter air passage. Later HS versions had the wider 1 1/4 diameter passage. The air flow meter can be used with 1 1/4 inch and wider carbs.
John Twist at University Motors on Youtube has instructive videos on H-type carb adjustments.
Successful H-type carb adjustment is dependent on proper jet centering. If the jet isn't centered then the needle doesn't move freely. Look to John Twist for the best video on H-type et centering. Even then, it is much, much more art than science. H-type adjustment instructions are based listening and feelings.
The H type carbs has several cork parts that eventually dry and crack - creating air leaks that make proper adjustment difficult. The H-type jet bearing assembly contains three (maybe two?) cork parts. There are failure points.
The final prominent H-type issue is air leaks at the throttle shafts. The soft metal brass shafts are brass and do wear. The softer metal housing on the throttle body can wear (even though not as much as many casual observers believe) requiring the throttle body's "re-sleeving." Air can leak in through the gaps worn between the throttle shafts and throttle body. Replacing worn throttle shafts (with similar-sized replacement shafts) is often sufficient to address the problem. "Re-sleeving" with new shaft bushings is often recommended. This service costs a minimum of $50 per throttle body - plus shipping.
Bottom line: Effective H-type adjustment depends on eliminating air leaks (from shafts, throttle bodies, and cork pieces in the jet bearings) and properly centering the jet. Eliminate these issues then you can move on to jet and choke adjustment (mostly jet adjustment). Common adjustment tools (air flow meter and carb synchronizer) have very limited use with H1s because the tools are too large for the H1's 1 1/8th air flow opening. The guys I've assessed as most effective (and I've seen in action), can "feel" when the carbs are in adjustment. On H's that will be the best one can ever effect."
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