1978 390AMX/CR Carbie Jetting

[Colin Jay]

I am in the process of resurecting my old 1978 390 AMX (damn you VMX magazine). I have found most of the bits in various box scattered throughout the shed, but have run in to a minor problem with the carbie. At one point I had the carbie fitted to one of my TT500 Yamaha engines, and the jets were changed to suit the 500. I have looked in both my parts and workshop manuals and been able to find the correct jetting for the 390 engine with the exception of the size/number for the needle. Can anyone tell me what the original/correct needle is for a 1978 390?

CJ

[PEZBerq]

Yeah the manual doesnt list the needle fpr some reason.  Mine runs a 6DH3 needle on 3rd clip position with 420 main jet, 2.0 air jet and 25 pilot jet. Goes like a rocket I reckon Beware of the feeble kickstart lever splines - although you sound like you had a good run back in the day so know how to keep em tight.

[Colin Jay]

Thanks for that, I just went and had a look in my box of jets and I have a 6DH3 needle in the assortment of needles, so it will be going back into the carbie.

 I can confirm the problem with the kickstart shaft, having sheared one back in the day. It really makes your day when you break one, as there is no way you will ever start the bike with out one.  I had the broken one welded up and used to carry it as a spare, just in case. Maybe I should look at buy another new one, just in case.

CJ

[Pedro]

Yeah the manual doesnt list the needle fpr some reason.  Mine runs a 6DH3 needle on 3rd clip position with 420 main jet, 2.0 air jet and 25 pilot jet. Goes like a rocket I reckon Beware of the feeble kickstart lever splines - although you sound like you had a good run back in the day so know how to keep em tight.

  Yep the Berq is on the money but I have found a bigger pilot jet will make it start better when its hot a 35 or 40 when you get it going check the plug it will tell you whats going on should be baby biscuit brown and he is right about the kicker if you fit a decomp. valve in the head it will make things easier for you and the bike. How about some pics on your progress .
                                 Husky AU

[Colin Jay]

Interesting about the size pilot jets you use. My spare parts book and owners manual list a #45 pilot jet as being standard, and that is what is currently in the carbie.

CJ

[PEZBerq]

I cant seem to get them to run properly with the bigger air jets. I always end up with a 20 or 25 to stop the blubbering  .  Run sweet after that. Starts well - choke no - throttle cold, no choke - some throttle hot.  I use Castrol TT at 3% i.e 32:1 with Champion N3C plugs. Works for me anyway. Lets see the Phoenix rising