Motorcycle Carbs
Modern machines
Comprehensive Overhaul.
Bike carburettors: Post 1990ish to date (Picasa Gallery - opens in new window)
General notes:
Whilst the basic physics have not changed over the years, the modern carburetor is the result of a period of evolution that since the 1970’s, has taken us from the slide carburetors of those years, that were “tall”, bulky, heavy, mechanically complex instruments, yet of limited efficiency- to the present day instrument that is compact, light and vastly superior in most respects. Over this period, the engine designer has demanded carburetors that did not limit his technical choices thus high intake angle, compact engine size, V4 configurations, light weight etc allied with fuelling efficiency and performance have all been accommodated by carburetor manufacturers.
The future of motorcycle engine fuelling is fuel injection :- whilst physically compact, fuel injection and digital engine management allow a level of engine efficiency, emission control and power output that is simply not possible from a carburettored engine. Such equipment and specification is already common at the “sports” end of most manufacturers’ ranges.
Digital engine management was commonplace on motorcycles before the fitting of fuel injection, thus many of the controls and sensors that are a requirement of digital engine management systems have been built into and onto the traditional carburetor form. An understanding of their function and operation is a requirement when overhauling these instruments.
For a carburettored engine to work to its full potential, the instruments need to be in the best possible order - properly adjusted and internally clean. Modern fuels are a major problem in that they separate out very quickly leaving contaminating residues within the carburetor body. The results of this contamination range from indifferent engine performance to non start.
The modern machine spends a lot of time parked up. Whilst often occasionally used it is obviously important that when needed, it starts and performs to its true potential.
When your bike won’t start, or runs poorly (yet is mechanically and electrically sound) you have choices to make as to how to resolve matters.
Your dealer may not have the time, experience or the equipment necessary to complete carburettor overhaul work as well as you (or they) would like. Many main dealer “workshops” diagnose problems by part substitution but this will not rectify carburettor problems (other than to possibly confirm the problem lies with the carburettors). Your dealer may of course prefer to sell you a new set of carburetors, take the 10% parts profit, charge you to remove the old ones and fit the new and then sell your old ones on!!! On a four cylinder machine, expect £800 plus for the carburettors and possibly a £1000 bill? Or he may suggest a new bike!
On the other hand you can send your carburetors to JRS. You could ask your local dealer to remove the carburettors and send them to JRS. Many already do.
You can save even more by taking them off your bike and sending them yourself.
All work is completed as stated below. No doubts, no confusion, just an engineering approach to carburettor overhaul, cleaning and maintenance. With the completed work you will receive a letter confirming what has been done and bringing any matters that are relevant to your attention.
On return, they are refitted to the machine. Connections for throttle and fuel are completed and the engine is started. Final synchronizing is completed with gauges and the idle mixture screws are set. That is it. Notes on carburettor related matters are also returned with your work.
Method
When work is received it is washed to remove all external residues. Multiple applications are dismantled to individual carburettors. Each carburettor is fully dismantled (CV units down to the butterflies). All parts are cleaned and rinsed in ultrasonic baths. All components are then air dried at 200 psi and at that point carefully examined. At this point you are advised if anything requires replacement or attention and you decide on what, if anything is to be done. Each carburettor is then carefully rebuilt, static settings are built in and multiple applications are reassembled. Linkages etc are lubricated and the carburettors are visually synchronised.
The completed assembly is tested for fuel tightness after which it is carefully repacked and returned to you with a letter that confirms the work completed and the condition of the carburettors.
Turnaround
7-10 working days
Comprehensive overhaul costs. Packing and insured return carriage is included in all of these prices
Singles £ 80
2 £150
3 £225
4 £300
6 £450
Parts
If you wish to use any of the JRS services detailed on this page, or would like further information, please contact Mike Davies at JRS.
Tel: 01792 402458
E-mail: jrs@jrs.uk.com
