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Maxim 400 help Please!
- Thread starter User9053
- Start date
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- carburetors exhaust
Do what works for your bike
No it's not strange, like chris said every bike is different. It also depends on stuff like your altitude (thinner or thicker air) and local fuel composition. I believe mine are also out 1 - 1.5 turns
My next thing is to change the jets. The PO must have jetted the bike when they put the Mac system on but they put 2x 127.5 jets in using the stock airbox rather than staggering them. I have a feeling one cylinder is getting enough fuel and the other getting flooded
If your jets are too big it won't cause flooding. If the main jets are too big you'll run rich at high rpms and possibly experience "bogging" where the engine won't want to turn any faster; it's like hitting a "wall." All of a sudden the engine will be pulling hard through the range and you'll suddenly be tossed forward a bit as the weight shifts forward. It feels almost like hitting redline on a vehicle that actually prevents you from crossing it.
If you're flooding look to your float height or float needle (the small needle that hangs from the float and blocks the fuel from coming into the bowl). Also, check your petcock. It should be on ON, not PRIME. If your petcock is on ON and flooding there is a leak. The stock petcock is vacuum operated and fuel should only pass through it when the engine is running with the ON position selected. If PRIME is selected fuel may pass through the petcock even when the engine is not running.
If you're flooding look to your float height or float needle (the small needle that hangs from the float and blocks the fuel from coming into the bowl). Also, check your petcock. It should be on ON, not PRIME. If your petcock is on ON and flooding there is a leak. The stock petcock is vacuum operated and fuel should only pass through it when the engine is running with the ON position selected. If PRIME is selected fuel may pass through the petcock even when the engine is not running.
You have a mac 2-1? Is your airbox stock? If this is so you're 1 size up on the left and 5 sizes up on the right. try stock jets. Your right side is outrageously large. This would cause problems at WOT as you described.
You need stock and at most 2 sizes up on each side. Two sizes up is a stretch in my opinion, but shipping is often so expensive I would hate to have to reorder a second time for such an inexpensive item. You said the idle and mid range is perfect? You shouldn't have to touch the pilots then unless you plan to "upgrade" to pods in the future. Think about your end game and save yourself a lot of shipping. MikeXS for example has a decent minimum shipping charge that will sting you if you're only spending $4 at a time. The waiting would also drive me nuts.
I went from a very free flowing 2-2 exhaust to a mac 2-1 and I had to further reduce my main jet size (i keep the baffles in the mac). The mac 2-1 flows better than stock for sure, but it's main advantage is how crazy light it is.
I went from a very free flowing 2-2 exhaust to a mac 2-1 and I had to further reduce my main jet size (i keep the baffles in the mac). The mac 2-1 flows better than stock for sure, but it's main advantage is how crazy light it is.
You can get the china made jets at yamaha now for the same price that mikes has them.( at least mine does) If you can I would go with genuine mikuni jets they will work much better than any knock offs.
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Ok so I went 127.5 left and 117.5 right. Wow what an amazing difference! Way more power and it actually wants to get to redline now. I'm noticing a little bog so I think I'll go back to stock 125 left 115 right and it should be right. Now just to tackle the low end. I still have hesitation below 2.5k so I guess I need new pilots. The question is do I go lower or higher? The bike seems to run better at 1.5 - 2 turns on the pilot screws but then doesn't idle very well. I just want to minimize the times I have to remove the carbs. I also get popping on decel. Does that show rich or lean on pilot circuit? Thanks guys
Popping on decel usually means you're a little lean in the pilot circuit.
Yes, it sounds like your main jets are still a little too big, going back to stock 125/115 will probably cure that.
You should be very systematic about what you do and only change one thing at a time. Do the main jets first. Start with tuning the highest rpms at WOT first, then do the mid range, then do the lower range, then do idle.
You also need to make sure the carbs are synched very well. I had to do this more than once to really get things right.
The bad news is that you might be removing the carbs several more times. The good news is that you'll get very fast at it. This is the price you pay for using aftermarket parts.
Remember, start at the top and only change one thing at a time.
I would leave the pilots alone and just fix those mains first. Test ride the bike and observe. Once the higher range is sorted I would hit the idle systematically. Adjust both idle mix screws by a full turn in an arbitrary direction (just remember, or better yet write it down) and test ride it and observe. Now, turn the idle mixture screws a full turn again in the same direction and test ride the bike again. Keep doing this until you see a clear difference. Do this and you will know for certain whether turning them out increases fuel or decreases it. I don't know anything about the maxim carbs, so I don't know if you have a fuel or an air mixture screw.
Yes, it sounds like your main jets are still a little too big, going back to stock 125/115 will probably cure that.
You should be very systematic about what you do and only change one thing at a time. Do the main jets first. Start with tuning the highest rpms at WOT first, then do the mid range, then do the lower range, then do idle.
You also need to make sure the carbs are synched very well. I had to do this more than once to really get things right.
The bad news is that you might be removing the carbs several more times. The good news is that you'll get very fast at it. This is the price you pay for using aftermarket parts.
Remember, start at the top and only change one thing at a time.
I would leave the pilots alone and just fix those mains first. Test ride the bike and observe. Once the higher range is sorted I would hit the idle systematically. Adjust both idle mix screws by a full turn in an arbitrary direction (just remember, or better yet write it down) and test ride it and observe. Now, turn the idle mixture screws a full turn again in the same direction and test ride the bike again. Keep doing this until you see a clear difference. Do this and you will know for certain whether turning them out increases fuel or decreases it. I don't know anything about the maxim carbs, so I don't know if you have a fuel or an air mixture screw.
