I put k&n filters and free flowing exhaust. took it to have carbs jetted. they had to go up on small about 5 sizes and about 20 on other. bike runs good on bottom and even better on top. the middle is not good. what to do? 1980 gs 450s.
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Re: I put k&n filters and free flowing exhaust. took it...
The middle range is controlled by the slide needle , so if you raise or lower it\ them a notch, depending on whether it is rich or lean when it is not so good.
If you try it with the choke on is the middle better or worse, this may help determinr if it is rich or lean
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the carby would have had the correct jet installed for the venturi size
It would have been better to leave it at that and then cut back in jet size
air filters do not affect performance unless they are blocked and it is a fact the so called high performance air filters let larger dust particles through and that cause a shorter engine life
mufflers can be changed to get better performance but it can be a trade off for noise
price is no guarantee of better so consider going to a bike shop that has a bike dyno and asking what muffler make and design will give the best increase in performance then have the bike tuned to get max performance from the muffler and new carby
the real way to get performance is not by guessing but by running the bike on the dyno so all performances can be graphed and improved upon
Hi, Gavin nice novella if you have changed your fuel delivery system, air filter size or flow rate, mufflers or exhaust system or a significant change in altitude your carburetors need re-tuning and if your fuel system (gas tank, filters, fuel valve and carburetor) is contaminated with ethanol sludge, varnish, rust, dirt, water etc. or your bike has been sitting for months or years without running these components must be "PROPERLY" cleaned and reassembled "CORRECTLY" before any adjustments can be made. Tuning your carburetor is fairly simple once you understand the basic principals. You engine is a simple airbox sucking air in and blowing it out, it is finely tuned at the factory for maximum performance once you upset that delicate balance by changing air filters, camshafts or exhaust systems your performance may go down the and the engine may run poorly, you need to compensate the air-fuel mixture in the carburetor in order for the engine to run smoothly and at peak performance. If you are running multi carburetors you need to sync them first and make sure your air cleaner element is clean and dry for paper elements or lightly oiled for foam and meshed elements and properly installed. Here is how and where you compensate trouble: "TIP" if your engine "BOGS" your not getting enough fuel.
1. Closed to 1/8 throttle is managed by the air screw and pilot/slow jet.
2. 1/8 to 1/4 throttle is managed by the air-screw, pilot/slow jet, and throttle slide.
3. 1/4 to 1/2 throttle is managed by the throttle slide and jet needle.
4. 1/2 to 3/4 throttle is managed by the jet needle, needle jet, main jet, and air jet.
5. 3/4 to wide open throttle is managed by the main jet and air jet.
6. Wide open throttle is managed by the main jet.
If you are running lean, spark plug electrode color is white, engine runs hot and feels like it is starving for fuel you need to go up on the jet size or move the c-clip down one notch. If you are running rich, spark plug color is black or dark gray, engine runs cool, and bogs down when accelerating you need to go down on jet size or move the c-clip up one notch. When your carburetor is properly tuned for maximum performance your spark plug electrode will be a light tan color like coffee with cream. If you prefer fuel economy over performance you can go down on main jet sizes until a satisfactory level of lower performance is acceptable versus MPH, your spark plug color will be whiter and your engine will run warmer. These tuning adjustments will only make improvements if your intake and exhaust system have no air leaks or sealing issues and the entire electrical system is in proper working order and you have no mechanical issues. For more information about your issue and valuable "FREE" downloads that you will need please click on the websites below. Good luck and have nice a day. Life On 2 Wheels 50cc GET Carburetor Basic Tuning PEUGEOT SpeedFight 3 Workshop Manual Browse Product Categories PEUGEOT Speedfight 2 Owner Manual
Your bike is running too lean. If you have not made any changes to the air intake or exhaust then your pilot jet may have something blocking it. (probably a piece of dirt, or just tarnish build up of fuel if the carbs aren't drained while in storage) By turning the choke on, you are reducing the ammount of air allowed into the "Fuel / Air" Mixture. This allows the bike to idle properly. Once the choke is off, the mixture has too much air and not enough fuel causing the backfire. If you haven't changed anything like the exhaust or air filter it sounds like a good carb cleaning is in order. Otherwise, you will need to change jet sizes to accomodate the difference in air flow.
You are dealing with Suzuki vacuum carbs, you cannot just replace the air box and re-jet. What you are running into is there is no pressure to raise the diaphragm because there is no restriction to create such vacuum. Either put the stock box back on or go to the biggest main jets you can buy. Sometime even when you get stage 3 jets you still have issues. Vacuum carbs are not made to run with no restrictions.....putting aftermarket exhaust on it will make things much worse.
general rule of thumb is to go up about 10 jet sizes,unfortunately it is a bit of trial and error,and you may have to swap out diferrent sizes to get the bike running right,(jets are quite cheap though)but first step about 10 sizes from standard,your local dealer should be able to tell you what jets are in it and supply replacements,if you change to a hgh flow aftermarket air filter you may have to change jet sizes again as changing the filter may effect the mixture ratio in the carbs,,hope this helps
must the exhaust be specific to the model is there no way to take an exhaust made for a similar scoot and fit it to the scarabeo?
What is your goal? The scooter exhausts offered by Leo Vince and Malossi aren't actual performance systems. People use them because they want to customize the scoot or get more of a growl sound while also passing emission inspections. Most people in the USA never have an emissions inspection on their scooters and are thus free to bolt on any exhaust they choose. If you are looking for performance you need an aftermarket free-flow system like those used for off-road bikes and your only limitation is how loud of an exhaust you are willing to accept. There are plenty of aftermarket exhausts for pit bikes and small dirt bikes that should bolt on to the S100-4T.
Personally I would start by looking at mods people have done on the Honda XR70 since it's about the same size engine and uses the same 20mm Keihin carburetor. Of course if you bolt-on an aftemarket free-flow dirt-bike exhaust you will need to replace the existing restrictive airbox with a free-flow K&N unit and either add larger jets to the existing carburetor or switch to the high-flow 20mm PE Keihin or the 24mm Keihin. Either way, the muffler is the easy part it's getting the fuel/air mix right and that's all carburetor work.
have a VR 2000 Supermot and when I bought it the guy had taken off the air filter and box and put a racing exhaust on it. I dont know what other modifications he could have done. Anyway we put the original exhaust back on and just fitted an airbox with K&N air filter and it starts and ticks over fine and runs fine up to about 3 thousand revs and then it kangaroos (stop and start) and it stalled at one point. I checked and there is fuel in the tank. The fuel feed must be ok coz it ticks over and revs fine when stationary. I have a theory that the guy who modified it has put big jets on the carbs to give better air/fuel mixture. Would this explain whats happening? How can I fix it? Thanks for your time.
i've been repairing dirtbikes and fourhwheelers since i was 12 with my dad, it sounds like a problem with the jets in the carburetor possibly one clogged with even the smallest piece of dirt will cause this, also how old is the bike, this sounds alot like a problem i had with an old dirtbike, sitting stationary the bike would run like new, yet get on it and put the engine under a load it would start sputterin and runnin like complete garbage, the bike was an 87 bw200 and after messin with the carb i ended up buyin a new one cause it was internally clogged but if its a newer bike i'd definently check the jets, and if you cant figure it out, then a local bike shop could probably diagnose the problem, if you have friends with bikes get suggestions from them on a good local place,,,