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Poor Power <2500RPM Adjusting Carburetors and Valves?
- Thread starter robbiecampbellsoup
- Start date
robbiecampbellsoup
XS400 Enthusiast
So I flushed the engine with a bunch of thin motor oil, about 5-6 times. Hoping that will have done it.
Rebuilt the head and replaced all the gaskets, new rings, new valves, new valve guides, 2 new valve seats.
Now I need to order some shims at the moment - anyone have a good Canadian source?
I'll be calling the local dealers tomorrow (all closed today!) hoping there are some Kawasaki or Yamaha mechanics with parts in stock.
Looks like I need 2x 2.40mm and 1x 2.45mm.
Almost finished welding up the frame - just need to make an integrated rear fender on the swing arm, then paint everything. I'm going to attempt to spray it myself, primer, and thin layers of black paint, then a clear.
Any suggestions regarding paints? Should I go with a high temperature product? I'm mostly looking for easy coverage and decent durability.
After that - finish putting the engine back together (Valve shims and top end gasket). Then I need to paint it... kind of afraid of this step. It's obvious as seen from the attachments that there are two different paints on it at the moment. I'd like to get it all one nice tone. The bottom end and top end need to be stripped of the current paint and then all needs to be painted.
Does anyone have any reservations with simply stuffing holes, using aircraft remover, meticulous masking and then priming and painting? Will the solvents kill the gaskets? I'm scared of this step...
-R
Rebuilt the head and replaced all the gaskets, new rings, new valves, new valve guides, 2 new valve seats.
Now I need to order some shims at the moment - anyone have a good Canadian source?
I'll be calling the local dealers tomorrow (all closed today!) hoping there are some Kawasaki or Yamaha mechanics with parts in stock.
Looks like I need 2x 2.40mm and 1x 2.45mm.
Almost finished welding up the frame - just need to make an integrated rear fender on the swing arm, then paint everything. I'm going to attempt to spray it myself, primer, and thin layers of black paint, then a clear.
Any suggestions regarding paints? Should I go with a high temperature product? I'm mostly looking for easy coverage and decent durability.
After that - finish putting the engine back together (Valve shims and top end gasket). Then I need to paint it... kind of afraid of this step. It's obvious as seen from the attachments that there are two different paints on it at the moment. I'd like to get it all one nice tone. The bottom end and top end need to be stripped of the current paint and then all needs to be painted.
Does anyone have any reservations with simply stuffing holes, using aircraft remover, meticulous masking and then priming and painting? Will the solvents kill the gaskets? I'm scared of this step...
-R
Attachments
robbiecampbellsoup
XS400 Enthusiast
So - I've done a bunch of work since I last posted.
Here's where I'm at right now.
currently running 145 Mains, which seem too rich, (I had to drop the needle to the leanest setting to get it to run well b/w 1/8 and 3/4 throttle). Under full throttle it still bogs down a bit. I put in 132.5 Mains (next size down I happened to have) and it was definitely lean. White plug tips and all.
Just thinking over the seat construction and getting that sorted.
I've re-done the electrical and made a battery box.
Here's where I'm at right now.
currently running 145 Mains, which seem too rich, (I had to drop the needle to the leanest setting to get it to run well b/w 1/8 and 3/4 throttle). Under full throttle it still bogs down a bit. I put in 132.5 Mains (next size down I happened to have) and it was definitely lean. White plug tips and all.
Just thinking over the seat construction and getting that sorted.
I've re-done the electrical and made a battery box.
robbiecampbellsoup
XS400 Enthusiast
So I've re-jetted and the following runs decently well;
I've used GTIDave's Carb risers to space out the UNI filters, and the bike came with a MAC 2-1 Exhaust
Mains: 142.5 Mikuni Brand
Pilots 45
Pilot screw 1-3/4 turns out from bottom
Plug chops at full throttle, and 1/2 yeild caramel brown/dark brown plugs
One thing I have not done is replaced the plugs in a while, or gapped the current ones to spec. Does this have a big impact?
The bike pulls well between 2000-7000rpm and kind of tapers off after that, it's stupid loud with this exhaust, almost too loud. I kind of want to stuff it with something, but then I also don't want to re-jet.
Can anyone provide any insight on the MAC exhausts and their powerband, as well as the effects of packing a pipe?
The bike is getting close!
I've used GTIDave's Carb risers to space out the UNI filters, and the bike came with a MAC 2-1 Exhaust
Mains: 142.5 Mikuni Brand
Pilots 45
Pilot screw 1-3/4 turns out from bottom
Plug chops at full throttle, and 1/2 yeild caramel brown/dark brown plugs
One thing I have not done is replaced the plugs in a while, or gapped the current ones to spec. Does this have a big impact?
The bike pulls well between 2000-7000rpm and kind of tapers off after that, it's stupid loud with this exhaust, almost too loud. I kind of want to stuff it with something, but then I also don't want to re-jet.
Can anyone provide any insight on the MAC exhausts and their powerband, as well as the effects of packing a pipe?
The bike is getting close!
Have you tried smaller main jets? The DOHC doesn't appear to require large main jets. My exhaust was also very loud when I was running rich. I'd suggest decreasing the main jets to 125 and test from there.
robbiecampbellsoup
XS400 Enthusiast
I put in 132.5 main jets and it was running very lean according to the plugs - see the pic above. That was with trying the needle in both rich/lean configurations.
Another note is that when I had the 132.5 mains in, the top end lost power and stuttered at full throttle.
One thing that I am noticing is that the carbs make a noise on applying throttle off idle, almost like a weird suction noise, I had heard in conversation this may be a sign of something, though I could not recall if it meant lean/rich.
Another note is that when I had the 132.5 mains in, the top end lost power and stuttered at full throttle.
One thing that I am noticing is that the carbs make a noise on applying throttle off idle, almost like a weird suction noise, I had heard in conversation this may be a sign of something, though I could not recall if it meant lean/rich.
The spark plug pic in post 63 shows a plug that is very rich. I'm going to stick with my suggestion to try 125 main jets.
Sesty
H.E. Pennypacker
plus well oiled uni filters aren't as free flowing as you would expect.