Changing Jets?

[firefightermatt]

Hey guys I just ordered my exhaust for my bike and am going to order the Suzuki 125 & 35 jets for the carb. I have been looking for a write up with pictures showing how to change the jets but have had no luck yet. I have no experience with carbs and have no idea how to change the jets so if anyone knows of a link to a write up that would be great.

Thanks,
Matt

[forchetto]

Drain the fuel from the carb by shutting off the main tap and opening the drain screw at the bottom right hand side. The fuel will run out through the drain hose. Place a suitable container under it.

Ideally you should be able to change the jets without removing the carb from the engine. There's enough clearance under the carb for access using short handled screwdrivers. The bad news is that the four little M4 screws that hold the float chamber are incredibly tight and the chances are that you'll round them off before they come out.

I had to remove the carb and use an impact driver. Not nice in such a delicate instrument such as a carb. Once the float chamber bottom is off, turn the carb upside down, taking care with the float assembly. This is a very fragile component and any knock could throw out the fuel level setting.

If you're going to handle the carb a lot, remove the hinge pin (just pushes out), that hold the floats and needle valve in position, and put it somewhere safe.

Use good fitting screwdrivers on the jets, try the drivers on the new jets first to ensure they fit well before you attempt to remove the originals. They're not on too tight but, being made of brass they burr easily.

This photo shows the positions of the jets. The Main one also has a washer behind it that is easily lost. Watch out for it falling down as the main jet is withdrawn.

The slow jet is fitted inside a sort of tube.

Count the number of turns your mixture screw is out for. Screw it in completely counting the turns until it bottoms gently. Don't force it or the needle-like end will get damaged. When you have the new slow jet in, this screw will probably only need to be unscrewed by 1/2 to 1 and 1/4 turns out. This is because the slow running circuit will have a lot more fuel through it now, due to the bigger jet.

I couldn't find a picture of our carb, but this one is similar. The differences are that the idle mixture screw on ours is at the top of the carb, next to the inlet manifold and the slow-speed adjuster is also at the top.



There are several tuning guides about, like this one (a bit complicated!)

http://www.factorypro.com/tech_tunin...m_engines.html

[david3921]

This is how I did mine without taking it out of the bike;

http://web.mac.com/danoaks/www.dirtly.com/Rejet.html

It's same website that forchetto found with reguard to the risers.

[forchetto]

This is how I did mine without taking it out of the bike;

http://web.mac.com/danoaks/www.dirtly.com/Rejet.html

It's same website that forchetto found with reguard to the risers.

Brilliant little guide there, thanks. I notice they had trouble with the screws and have replaced them with allen headed ones.

It was only after struggling with the original ones that I read a tip that could be useful when dealing with tight cross-head screws:

Dip the tip of the screwdriver in a little fine grinding paste, of the type used to re-grind valves. This increases their grip no end and prevents the driver slipping out.

[firefightermatt]

Thanks guys! That seems to explain it pretty good...I just hope I dont run into any problems trying to tune it with the mixture screw.

[firefightermatt]

Hey guys I was looking through the service manual and if you look on page 109 it says our carb has a 127.5 main jet and a 32.5 pilot jet. Does it really have a 127.5 main because I just ordered the 125 main and I wont want to use it if its smaller then stock.