5. Carburettors, jetting & sparkplugs

Assembly manual

5. Carburettors, jetting & sparkplugs
Richard Taylor wrote this manual.

The conversion will accept most small body 24-25mm carburettors that use a flexible rubber mounting. Check the clearance of the carburettor before committing to purchase. Two of the obvious makes that work well are the
following:

GT186 small block, 25mm Dellorto. Part number: PHBL25. Cable choke conversion Part number: 53003 With air box. We would suggest between a 93-97 main jet and B7 plug, 50-55 idle jet, AQ266 atomiser, 40 Slide and
D22 needle. Without air box & filter. We would suggest a 102 main jet and B7 plug

GT186 small block 24mm Mikuni flat slide. Part number: TM24, 001-017. Cable choke conversion MK-412 With air box. We would suggest a 185 main jet, 17.5 Pilot jet, Top clip on 5d h7 needle, 1.5 turns on mix screw with
B7 plug Without air box & filter. We would suggest a (TBC) main jet with B7 plug

GT186 small block Other carburettor options for 30mm manifold: Dellorto VHSH 30 flat slide with cable choke conversion Part number: 53003
Settings for open mouth with Franspeed race. Suggested jetting between 135 – 145 main jet, DP268 (or DQ268) atomiser, U2 needle, 55 slide, 35 idle jet, B35 idle emulsion tube. Timing set at 17 degrees BTDC.

GT186 small block, Mikuni TMX30 power jet, Settings for open mouth with Franspeed race. We would suggest between 220-235 main jet.

GT200 big block, Dellorto PHBH30 (caution standard version of this carb has restricted access to air screw and idle stop adjustment when fitted to R/H manifold) Cable choke conversion Part number: 53003. Settings for open mouth with Franspeed race. Suggested jetting between 130 -135 main jet, AV268 atomiser, X13 (or X7) needle, 40 slide, 55 idle jet, Timing set at 17 degrees BTDC.

Caution: Be aware that exhaust systems do vary in their jetting requirements, these jet settings are only a guide. It is important to check the spark plug regularly to insure the jetting is correct. On long runs it is always advisable to
increase the oil mixture, in all cases the plug colour is the principle indicator. Remember that if your jetting and plug colour was correct in winter and spring it will need to be check again in summer or prolonged hot periods.

Be aware that different sparkplug numbers have different properties, hot or cold running types. We recommend that you settle on one make and change plug according to the ambient conditions. We would recommend starting with a cool-ish running plug such as a NGK B7 SE.

A note on Exhausts.
Changing exhausts will change jetting and some times timing too. If you change exhausts we recommend you monitor your jetting again. Additionally, if you use an expansion chamber, we recommend you retard the ignition
timing to 17 degrees.

Section index

1. Pre-fitting kit preparation
2. Installation preparation
3. GT186 Stock Touring Installation steps
4. Air box installation amendments
5. Carburettors, jetting & sparkplugs
6. Running in
7. Care and Maintenance
8. Tuning & performance
9. Disclaimer
10. Trouble shooting
11. Cylinder head specifications
12. Suggested specifications