Going from a high comp piston (stock bore) and midrange cam TO a 102mm high comp piston, full port and polish with larger valves....... approximately how much should I raise my jetting? I am currently running 150/155 DynoJet jetting. What would be a safe start on jetting for break in? After full break in, it will be put on a dyno to tweak jetting.

Thanks for any input, I am new here and was told that I could get some good info from this site!
Sneekee.

 

Try 175/180. better to start rich then lean, may also want to go a click richer on the needles ( up i think? ) and up another size on your piolits, to 27's.

 

Thanks Fatty for the suggestions, and I appreciate the quick response! I do now currently run the 27.5 pilots, that's one less change. LOL

I assume this thing is going to take in much more fuel with the P&P, will the 175/180 still be on the "safe" side??

Any suggestions from some 686 riders out there, with first hand experience? I just wanna be safe..... not sorry!

Thanks again Fatty!!

 

TTT.........

 

I would think that jetting would be pretty safe to start at. Maybe alittle richer if you think you need it. Just listen for any back firing or anything when you first run the bike. Also watch your spark plug. I would like to help,but I run 35mm FCR's on my 686.

 

Thanks guys!!
I guess I'll start off with the 175/180 till I can open it up and check the plug, then I'll go from there. It'll be on the dyno within 2 weeks.

 

I have a 690 with porting,bigger valves and high comp piston and i use 175-180 mikuni mains.My air filter is a pro design foam and this jetting is for sea level but should work well up to about 2000 feet or so.The mikuni mains are different than the dyno jet numbers so keep that in mind also.

 

Good luck, tell us how it goes.

 

Good luck and keep us posted!

 

That's some good info duneittilludie! I wonder how the DynoJets compare to the Mikunis..... don't the DynoJets flow a little more? I might be able to run the 170/175's once I'm broke in?!? I also run a foam Pro Design filter. Sounds like our set up will be very close to the same.... what cam are you running?


Fatty, I'll definitely keep y'all posted on how it goes! Maybe even share some dyno #'s for sh_ts and giggles! LOL