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Carburettor Cleaning & Refurbishment - Harper's Ultrasonic
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Jota Carbs

We recently cleaned a set of Dellortos from a lovely original Laverda Jota, the owner was keen to retain the patina of the carbs and no plating was carried out. The result was still a stunning set of carbs, here are some pictures of Matt preparing to fire up the beast after the refit.
 
 

Replacing the Irreplaceable!

Sometimes a carburettor needs a replacement part that is not available or only available as part of an expensive assembly. Take the last type of carburetor fitted to the GSXR750 on the T/V models or SRAD, these have an arrangement where the needle slides in a plain brass tube fed at it's top end by a gallery from the emulsion tube. The emulsion tube sits inside the main jet holder and is fed by a gallery from an air jet in order to mix the flow of fuel from the main jet.
 
This all sounds complicated, but it gets worse; the emulsion tube is a brass part permanently pressed and bonded into the carburettor body casting - big bucks to replace!
 
Imagine our horror (and the customer's) when we last worked on a set of these to find that one emulsion tube (on #1 carb) had been rotted at the point it entered the body casting and the resulting expanding corrosion had blown through it's wall. The part was left dangling when we removed the jet holder.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
In the picture above the emulsion tube is missing from the left hand carb body, at this point it was decided to try a repair strategy that would entail removal of the remains left in the body casting and employ a section of custom made brass soldered to the remaining part of the emulsion tube in order to preserve it's dimensions.
 
To extract the remaining stub of the emulsion tube we wound in a suitable tap until it hit the bottom of the hole and gently eased it out. Below you can see the remains of the emulsion tube and means of extraction.
The brass had waisted quite badly at the point where the tube enters the body of the carb, so the stub was discarded and a new section manufactured on a high precision miniature lathe - the vintage Cowells 90E used in our workshop.
At this point the blank tube was attached to the existing emulsion tube and sized to match the height, internal Diameter and External diameter of the original part. One cross hole had been lost to the corrosion and was carefully drilled using a special self-reaming carbide drill bit in a cross-slide mounted milling vice. The newly restored part was then burnished and cleaned inside and out in a special solution to neutralise any by-products of the soldering process.
 
 
 
 
 
 
 
 
 
 
 
 
Once we were happy with the finish and accuracy of the repaired part it was offered up for a final check, then secured in the body with a thin smear of epoxy bonding material; the latter is the same product as used by some engine tuners to re-shape inlet ports on high performance cylinder heads and as such it is well tested in hot environments where fuel is present.
 
To ensure a good bond the hole in the body was cleaned out to remove corrosion and ensure that sufficient epoxy remained in the joint, the portion of the emulsion tube to be bonded was also gently knurled using a small coarse file in order to retain the epoxy and centralise the part in it's bore.
 
Once set the assembly was checked for concentricity and height compared to the adjoining carbs and the reassembly of the remaining parts completed.
 
I will let the customer's comments on the finished job complete this post:-
 
"All's well that ends well.... the refurbished carbs were fitted to the bike, & aside from balancing / synchronising, there were no other issues..............Thanks again, a great job & I'll definitely be recommending your service to my biker pals ;o)"
 
 

Monobloc Refurbishment

Some time ago we did a set of Amal Monoblocs for a gentleman who is restoring a BSA A65 Spitfire he has owned for many years, the work involved fitting a major service kit from Burlen who market Amal carbs and spares which was a very satisfactory buying experience. See the finished carbs in the full blog entry.
 
We also Sourced many genuine new plated parts at a lower cost than replating the originals (which werre well worn in any case), the completed carbs speak for themselves in terms of the satisfaction the completed work generated.
 
They may not be just like new, but the original carburettors are retained instead of resorting to a parts shelf restoration.
 

Low Mileage Bike - Check This Out!

Today we thought we would share these photos of carbs from an '89 Kawasaki GTR1000 'Concours', the bike has 17,000 miles on the clock. These have been off the bike previously as they had accident damage from a drop and tumble (it looks like the bowls were off at the time), we also found a piece of elecrical; wire in one of the jets from a previous attempt to unblock it. Make up your own minds about the benefits of our cleaning service for low miles carbs:-
SDC11196SDC11197SDC11199
SDC11204SDC11198SDC11205SDC11201SDC11203

Challenge Carbs - The Results

Well here is the finished article, one carb cleaned in our special solution for corroded parts, the other left as it was, we will let you decide how effective it is when you take a look at the pictures. See the larger Resolution Pictures in our Gallery
 
XS250 CV carbs from the Corrosion removal challenge, destined to become a display peice. We are interested to hear from anybody who wants to see if we can revive some really badly neglected carbs!
XS250 Special Carbs - Before/After
 
 
 
XS250 Special Carbs - Before/AfterXS250 Special Carbs - Before/After
 
 
 
 
 
 
 
 
 

Challenge Progress

 
The carbs arrived a while ago at the Harpers' workshop and one half was subjected to our standard cleaning process for corroded parts. There was some significant problems associated with long term neglect; the choke shaft was seized solid in the bodies, both float valves were gummed into their seats and the end of the throttle cable outer was badly stuck in it's holder on the top brace.
 
Apart from the issues present, the float bowls were also missing, we suspect they had been discarded due to excessively poor condition.
 
 
After the cleaning process particular attention was given to rinsing and drying prior to reassembly, the change was astonishing and much rust was removed by the new solution; some brass parts that had also collected soft Verdigrise-like deposits had also been cleaned. The effects on brass were very good although surface colouring remained.
 
We hope to photograph the set once they have been reassembled to show the clean and dirty parts, the intention being to somehow seal the dirty carb with lacquer or similar and mount the pair for display to customers.
 
Keep watching this blog for the pictures
 
 
 
 

A New Year, A New Challenge

To date, nobody has presented us with any carbs that were beyond the powers of our equipment and cleaning solution, this includes a rather useful special solution that we only use for badly corroded parts.
 
We thought that as it is soon to be a new year we would try to push the limits of our expertise with a truly nasty set of carbs. Once the gauntlet had been layed down, we set about finding something to meet our own imaginings of the true horrors that could be lurking out there in sheds and back yards; in the end it was ebay that came up with these CV carbs off an Yamaha XS250 Special, lets hope they arrive...........
 
XS250 Special Mikuni CV carbs prior to ultrasonic cleaning with special solution for corrosion

Merry Christmas From Harper's

Well Christmas appears to have arrived in the workshop in the form of slow custom, so if you want a fast turnaround on carb cleaning, now is the time to get in touch. If your carbs need parts, this can be slower over the holiday period, but we do have some items in stock for FCRs and most common CVs.
 
The Harper's Ultrasonic Team wish all our customer's and friends a very merry Christmas and a happy new year.
 

Kawasaki 'Float Bowl Mod'

If you own a Kawasaki with Ram-Air fitted, chances are it would benefit from removal of the valve that shuts off the carb float bowl vents under certain conditions, there are many variations across different models and in the way the mod is done, but here is a nice simple example hosted by webzxr (Andy)
 
 

Mikuni VM - Simplicity

Many times I have dismantled a Mikuni VM carb and no matter what the size or configuration, it always strikes me that they are all that they need to be without any complications.
 
Last night I was working on a VM from one of my cherished but now dismantled 70s Suzuki TS125s, these bikes really show how little you need to produce an enjoyable and cheap two-wheeler, although as I remember, not very fuel efficient!
 
All that is needed to improve performance is a bigger VM and larger ports,it is surprising how much like the contemporary TM125 the major components are, unlike the more modern TS and RM models!
 
I was surprised how clean this particular VM was after years of use and storage, but there was the usual treacle residue in the float bowl prior to cleaning.
 
The carb is now in the pile of NOS and refurbished bits waiting for the day when I rebuild my 1975 TS125A
 
 
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Jota Carbs
Replacing the Irreplaceable!
Monobloc Refurbishment
Low Mileage Bike - Check This Out!
Challenge Carbs - The Results

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