OzVMX Forum

Marque Remarks => KTM => Topic started by: Tyrepower on March 28, 2012, 10:23:30 pm

Title: Jetting Help - KTM390 1981
Post by: Tyrepower on March 28, 2012, 10:23:30 pm

G'day guys, need a bit of help in getting the jetting on this beast sorted out. Can any one give me an idea on the starting points of what jets you are running in either a Mikuni Flat slide 38mm or a Mikuni VM 38mm round slide. I have one of each, with both way out of tune so need an idea of where to start to try and save a few hours. It currently has the flat slide fitted however runs rough and won't idle and tends to stall. Can usually do most mechanical work however the black art of carbs always freaks me out.

Cheers Richo.

Title: Re: Jetting Help - KTM390 1981
Post by: Slakewell on March 29, 2012, 06:42:37 am

I suggest that you buy a standard Bing on ebay there are a few tricks to sort out these great bikes and a flat slide carb isn't one of them. There are also two 81 model 390's is yours the big fin engine or the small fin?

Title: Re: Jetting Help - KTM390 1981
Post by: supermotomc on March 29, 2012, 07:06:23 am

well said !  go bing why run a car carb ridden ktm since 1978 and the only other carb we ever fitted was lectron that just IMHOP!

Title: Re: Jetting Help - KTM390 1981
Post by: Tyrepower on March 30, 2012, 09:40:03 pm

Quote from: Slakewell on March 29, 2012, 06:42:37 am

I suggest that you buy a standard Bing on ebay there are a few tricks to sort out these great bikes and a flat slide carb isn't one of them. There are also two 81 model 390's is yours the big fin engine or the small fin?

Please excuse my ignorance here........ I think its the big fin head. Now I only say that because the fins are bigger than what's on my TT500. I thought all KTM's had bigger than normal fins (Compared to Jap bikes) The reason I am asking about the Mikuni carbs is I have these on hand and don't have the original Bing. However I will look for a Bing on E/bay. Had a look today and found a few that might fit the bill, however none off a 390. So again any help on what size Bing and a starting point for the jetting would be appreciated.

Cheers Richo.

Title: Re: Jetting Help - KTM390 1981
Post by: oz555ktm on April 01, 2012, 07:42:48 pm

   Bing Carby - 38mm
                type -54/38/107 
          Main jet  - 185 or 190
        Needle jet - 276 or 280
        Jet Needle - 6L2
            idle Jet - 45 or 50
   Throttlre slide - 220
start Mix screw about 1/2 out and work from there

Title: Re: Jetting Help - KTM390 1981
Post by: supermotomc on April 02, 2012, 06:42:08 am

so for the daring 390 rider other data from tech data
                                                 Dimension X 2.0mm
                                                     ign timing 2.1-2.2      jet 185
                                                                                       276
                                                                                       6L2
                                                                                       45
                                                                                 slide 220
  now for the more exciting           Dimension X  0.8-0.9
                                                 ing timing 2.4-2.5           jet 175
                                                                                         274
                                                                                         6L2
                                                                                          45
                                                                                          220



so theses are  same bikes same year  different shipment ie container these were the 1600 dollar specials  that Bert got

Title: Re: Jetting Help - KTM390 1981
Post by: Tyrepower on April 02, 2012, 08:56:07 pm

Great, guys. Thanks for the help.

Sent from my rotary dial telephone...............