Hitchcocks Forum

Now the electrical problems are sorted on Henry, my 2000 Bullet 500, I need to get him to run right. Recently changed the 60`s style silencer for one of our hosts universal mufflers. Bike runs well up to about 40mph, then starts spluttering and running really rough. The Mikarb has standard 110 main jet, which worked fine for the last exhaust, but I think I need to up jet for this one. Just debating what size to go for. If memory serves, a rule of thumb is to go up 10%. The closest size to this would be 120, but wondering whether 125 may be a safer bet ?. Wonder too if I should be looking to upsize the pilot jet, though the bike seems ok at low to mid range. Funds are limited, so I want to try to get it right and not have to buy a few before nailing it. Sods law of course, a few years back I tried a K&N type filter and bought several sizes of main and pilot jets. Never did get it to run right, so put them away in the garage. Now I need them, they seem to have vanished !. Any thoughts/experiences with jetting for the universal muffler much appreciated.

Tomo I suggest you read this first:-.....................
http://www.hitchcocksmotorcycles.com/pi ... s_-_a4.pdf

Plus with the "universal" silencer you may need to raise the needle and have a slightly larger main jet.
(Allegedly that "universal silencer" can give you another three bhp.)

The main jet only controls mixture at 3/4 to full throttle. I would try lifting the needle a notch and see what happens. Also, do a plug chop and see what colour you have on the plug.

Thanks chaps. I have read the Hitchcocks carb notes, also understand that the main jet comes into use between 3/4 to full throttle. Thinking back it was probably nearer 50mph, maybe a little more when the spluttering started. Ran fine if I put on choke, so pretty sure it was a fuel issue. Think I`ll bite the bullet (pardon the pun)and order a 125 jet, see how that goes.

maybe this helps.

Get it wrong and you will start fouling plugs, modern vehicles are designed to run lean and the fuel is now deigned for this purpose, not for this old birdbath carby design, so it is more critical now than ever before to get it right, run lean and hole a piston,run it a tad rich and plugs become your next problem. Make sure you carry spare plugs with you while experimenting and remember, you foul a plug with this fuel you have to throw it out, they can't be reused

This sounds like you are going to fix it until it`s broken., listen to Norm. It`s best to leave it alone if you have limited funds. Some models break down without being fiddled with. Maybe get a Leggo set if you want something to play with. I am just trying to save you grief.

Mauri, thanks for posting up that chart, very useful. Leon, I gave up playing with Leggo 40 years ago when I first started riding and working on motorcycles. I am also a believer that if something works ok leave it alone, but read my posts, it is`nt !. I appreciate what Norm advises, but to be honest I would rather risk running too rich than too weak. I am pretty sure that the rough running is down to the exhaust change and the need to upjet, all I was asking was for opinions as to which size up from the standard 110 might be the best.

Hi Tomo: I understand your position and do wish you success with your problem. I was speaking from the "Been there done that" experiences in my youth, where I would pull engines to pieces to see what was inside, then find that they never ran the same after I put them together again. Maybe it was just me, I`m a failure. SIGH! Well, back to my Rubik`s cube.

Highly unlikely you jetting will be the cause of rough running