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Pipes 3&4 aren't getting hot like pipes 1&2 ???

lvin4jc

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This is assuming that the order is 1-2-3-4 from left to right as you're on the bike. The left two cylinders get the pipes nice and hot. The right two cylinders are barely warm when the left two will burn your hand with the slightest touch.

I had assumed that I had a bad coil but after doing some internet research it looks like 1-4 and 2-3 are pairs and fire together. Is that the case? If so then i'm confused because I believe 3-4 are the ones giving me trouble.

I pulled the plugs tonight, 3-4 were covered in gas and the pistons looked to be the same. 1-2 looked much better. However, all the plugs were so tight my gap gauge wouldn't even accept them. I opened them up a good little bit to get them to .025.

If what i've said above is correct, and that's assuming a lot, what else could be the problem causing weak spark?

Thanks!
 
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Plugs didn't look like they were struck by other parts did they?

Plugs closed that much cannot make full voltage, the gap largely determines volts. Provided rest of the system can supply them of course.

Ever done a compression test on this engine? Commonly no maintenance done has them leaking compression, that has same effect on plug firing as no spark.

Plugs once good and wet have a tendency to try to stay that way, you may need a couple more new ones until the engine gets sorted out to run on all 4.
 
I just ran to the shop and grabbed my compression tester and spark tester this morning. I'm hoping I'll have time tomorrow to use both.
I started it up this morning to verify that it was doing the same thing. Both left pipes burning hot, both right pipes room temperature, not even warm.
Hopefully ill report back soon with some numbers.
 
Alright, i'm going to get mixed reviews here and the news I have is mixed indeed.

First, the good. I put in 4 new spark plugs gapped to .030 and the bike runs much, much better. Actually, not only are all 4 pipes hot but the thing runs the best it has while in my possession. It has gobs of power, quick throttle response, it's just quick all over the place. It's my first motorcycle so I don't have much to compare it with nor do I really know how it's supposed to run in perfect condition. The best I can do is to tell you that it's as fast as my Honda 400EX atv which I always thought was fast.

Now for the part that's going to make you throw out what the previous paragraph says and question my judgement... I did perform a compression test. The results from 1-4 were 100-70-70-120. Not very good huh?

EDIT:

I ran across some threads that said you should test the compression with the throttle full open. I tested each cylinder again with the throttle wide open. Also, the engine was warm from my test ride once I got it running. Those numbers were 130-130-130-135.
 
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I like the fact you thought to check the temp of the pipes. Our basic senses are the most powerful diagnostic tools we have yet are the most often overlooked.

It seems you've already got things figured out but to answer your original question, the plug caps can go bad too.
 
I like the fact you thought to check the temp of the pipes. Our basic senses are the most powerful diagnostic tools we have yet are the most often overlooked.

It seems you've already got things figured out but to answer your original question, the plug caps can go bad too.

I'm not exactly sure why I checked that, I can't remember what led up to that but it was very helpful. I'm a car guy, pretty knowledgeable about cars but the motorcycle game is completely new to me. I will remember that this worked and use it again in the future for sure.
 
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