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Why would the front cyl. be leaner then the back. I have changed plugs three times, and the fronts are light brown and the backs are almost black.
Don Hurd
D'Ray
 

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Don Hurd said:
Why would the front cyl. be leaner then the back. I have changed plugs three times, and the fronts are light brown and the backs are almost black.
Don Hurd
D'Ray
Im no expert on this ,but heres a thought after having the same problem with my wifes 1300......check and tighten the large gasket,( rubber rings with the large clamps) that go on to the intake ...from the carb.. her's was loose. maybe sucking air and changing the burn rate.
 

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Mine does the same thing, I have no advise for you but I'm going to keep my eye on this post
 

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My front cylinder is slightly richer than the rear as well. I think it's pretty normal for a v-twin to be this way. Sounds like the difference in yours may be slightly excessive though. Good luck with it.
 

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the gurus will be along shortly but the rear plugs always seem to run darker..richer.....seen the posts on this tons of times but be damned if i can find 'em now....i know the crap board has a post with a really good plug color and explanation chart
 

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Anyone run a hotter plug in the front and a normal one in the rear to compensate for the difference? If so, what plugs are you using? I thought this might be a good option, just never knew which combination of plugs to use. Thanks for your thoughts.

MechE
 

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+1 As far as I know (I'm no expert) the front cylinder runs cooler.
 

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loud n proud said:
+1 As far as I know (I'm no expert) the front cylinder runs cooler.
That would seem to make sense. Even though the engine is water cooled the front cylinder is catching more cool air flow and the rear cylinder is catching mostly heat from the front cylinder.
 

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Yup - I figured the front one runs cooler also. It's been my thought that we don't have water cooled bikes, but rather water assisted cooled bikes (hence the fins on the jugs). Warm air exiting the radiator might raises the temperature on the front jug a little while the cooling fluid helps lower the temperature of the rear jug. If everything was balanced in a perfect world then both jugs would be running the same temperature.

But I have the same question. Has anyone used plugs of two different temperatures to compensate for the front one running cooler :?: I should probably go to a pro to jet my bike because it runs a little rich (particularly annoying when it is cold outside), but the sense of spending $250 for something I should probably learn to do my self someday seems a bit ^.

Or maybe Honda is using some "fuel cooling" to compensate. Don't laugh, they use this technique on air cooled aircraft engines. It is figured that about 10-15% of the fuel is unburned as it is used to remove the heat from those large cylinders.

Or maybe I should leave well enough alone :?

MechE
 

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stand outside with a garden hose running pointing atraight out then quickly step sideways where does the water go

the fuel droplets will lag when accelerating causing more droplets to go to the rear

also the position of the accelerator pump spray when turning the throttle

difference in cam duration/timing exhaust back pressure/pulses difference's
 

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MechE said:
Yup - I figured the front one runs cooler also. It's been my thought that we don't have water cooled bikes, but rather water assisted cooled bikes (hence the fins on the jugs). Warm air exiting the radiator might raises the temperature on the front jug a little while the cooling fluid helps lower the temperature of the rear jug. If everything was balanced in a perfect world then both jugs would be running the same temperature.

But I have the same question. Has anyone used plugs of two different temperatures to compensate for the front one running cooler :?: I should probably go to a pro to jet my bike because it runs a little rich (particularly annoying when it is cold outside), but the sense of spending $250 for something I should probably learn to do my self someday seems a bit ^.
Or maybe Honda is using some "fuel cooling" to compensate. Don't laugh, they use this technique on air cooled aircraft engines. It is figured that about 10-15% of the fuel is unburned as it is used to remove the heat from those large cylinders.

Or maybe I should leave well enough alone :?

MechE
The motor is a completely liquid cooled engine and the fins were just added to give the look. There is only a few bolts which hold the fins on and not enough to transfer much of the heat to the outer fins. The engine will operate within temp range just fine without the fins attached. I have seen numerous customs which utilize the 1300 engine with no fins (not the pretiest motor but relaible). Also it is the nature of a twin to run hot in the rear cylinder within reason.
 

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I still haven't seen a fact-based answer to the question posed by Don Hurd:
Why would the front cyl. be leaner then the back?
and to MechE's question:
Has anyone used plugs of two different temperatures to compensate for the front one running cooler?
I have the same problem: front plugs run brown and back plugs run black. It's always been that way on my bike. Is there an adjustment that we can/should do--other than re-jetting and other than gettyupgodaddy's suggestion of
check and tighten the large gasket,( rubber rings with the large clamps) that go on to the intake ...from the carb.. her's was loose. maybe sucking air and changing the burn rate.
Does anyone have a definitive link that we can look at or a definitive solution that we can apply? Thanks.
 
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