Not your typical Mikuni 38 mod

[kevbo]

Modding a 38 is seldom a good idea. At best you get very little. At worst you get to go through the entire tuning process only to burn a piston because one venturi was slightly larger than the other.

 

[Polish jet pilot]

Ok, thank you for these comments. So what is the best mod/list of mods to my OEM fuel system (starting from the carbs). I am about to drill/mill/and do terrible things to my carbs and afraid that I will mess them up.

I am mostly interested in things connected with machining since this is the hardest part.

Thank you

 

[kevbo]

If you don't sub the ski then get some free flowing flame arrestors and work on tuning the carbs. If you do sub the ski then use the stock flame arrestor and learn to tune. From there, get a tach and learn how to tune your pump. You will never be able to overcome the power loss from having too much pump load. Since you like to do machining, bore your nozzle.

 

[Polish jet pilot]

I do a lot of subbing. I have a scupper.

I havee currently oem inatke (chokes removed, 2 filter screen removed + R&D angled reed spacer), I bored the nozzle to 84mm, my prop is oem 2008, cutback by 2,5mm + wetwolf cone.

My cylinder is being bored right now to a 727 with porting for bottom end. I will have a hi comp head @ about 180 psi. I have a modded b-pipe too (bored, polished, etc)

I generally know how to adjust my carbs, I know the procedure. What I don't know is whether boring the carbs (v-type intake) and boring all obstructions and adding the atomizers will be good or not. Need input mostly here...

I understand that I will need to make jetting changes after porting is done, or can I stay with the jetting recommended 701 for B-pipe application? This is also of big importance to me. If you can advise - I will be obliged.

 

[MileHighJSC]

if you want to loose performance then go ahead and remove all the obstructions. JSS did this and many people had issues. Those ramps are there for a reason.

Some may already know this info, it coralates to BKs earlyer post. oem sj 38mm throats are not the same as retail 38s. Besides the chokeshaft castings there are other lumps casted in. These may be there to help with the signal, being that the low speed circuit has been purposly f**k up to be lean burn carb. I feel that if you want to machine your carbs you need to have the low end circuit modded as well to get all the performance you may be looking for. Comprable jetting I have found on oem sj38s is 70 and 135, retail is more like 67.5 and 110. The circuits delivering more fuel on the stronger signal on the aftermarket. Fact : More fuel will pass through the same size hole under pressure. In this case it in neg pressure (vacuum) but same theory. The low speed circuit is way different in the two carbs. More circuit outlets in a different spot. The deflection and blockage in the oem carb throat is double of the retail throat, out of the box (choke plates in). I think that if you really want to use your stock carbs leave them alone or send them to Art at Jet Works and have him mod them, He taper bores them and changes the circuitry.

 

[hre21]

if anybody has one of these for a 38 they would part with please let me know i sent my carb and had it machined and now the atomizer got lost in the process. thanks ,,anthony