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Discussion Starter #1
All, I've been having this problem since Summit and cant quite pin point it. I need to sort this out or I'm missing VC.

The bike revs and pulls great when cold, even under
load. Then with just a little heat, it starts to bog
at WOT around 6-7K in any gear, but only under load.
When it's cold or not under load, its revs perfect. I
haven't been able to do a plug chop yet? Floats and
float needles are good, petcock is flowing, carbs seem
good. I'm running stacks w/ no screens.

Need some guidance, could be I'm overlooking something...

Sotomoto
 

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Discussion Starter #3
Negative, I have Dyna coils w/ Bore-tek ignition. Check all my connections and everything looks fine, ground, etc...
 

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pampador-

yeah, with the stock engine stuff i think it's the valves that limit breathing to 105s, not the intake? i have v-stacks and i'm at stock jetting all around and it's running just about right. and i've been on alex's bike, it's only when hot and only when under load that it's bogging...but yeah it does feel like starvation under load. i'm hoping i get the chance to play with soto's bike this week.

-tt
 

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quote:Originally posted by pampadori

thats not typical with stacks. you need more fuel. the bogging is your bike leaning out.
Is that how the bike behaves when it's too lean; it starts to stumble and bog at high RPMs? That actually explains a lot. Are we talking about a CB350 here?

Many thanks. I'm always learning something.

--Chris
 

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Is it possible that your valve timing is off just a small tad so when the engine warms up the valve timing becomes affected??? I'm thinking that its bogging due to too much fuel - if it leaned out it would run really great until it ate itself. I'd look at either engine timing and/or valve timing.

I wanted to add, a plug reading will give you more indication (lean vs not lean). Run it up hot where it starts to bog then shut of the engine and stop to take a reading.

Keep us posted...
 

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Do a plug chop when the bike is warm with brand new plugs. Otherwise, we are just guessing. However since we are just guessing, I am going to guess that it is rich. Try going to a 100 if you can't get a plug chop done.

Ken
 

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i ran a plug chop for soto tonight. the bike was lean. i took off the ebay velocity stacks with the silly screen lips and the bike ran lots better...still a little miss at around 6K, but not falling on it's face anywhere (i'd be happy to race it as is). a second plug chop still shows lean but better. i just put some shims on the needles (cause i'm not ready to go to 110s) but it's too dark for another test run.

-tt
 

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tt,
If you took off the e-gay stacks and that richened it up, then you are not getting max airflow into your engine. Each engine is a mystery unto itself and if you need to go bigger with the jets, then that is what you need to do. I would not restrict my airflow in order to get correct jetting. I had to do that once at the track when I didn't have bigger jets with me. It ran clean but was down on top end at the end of the straight. I believe I have 120's in my 350.
Ken
 

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Gents:

What is a plug chop and how is it done?

Also, where are you guys buying your jets for the 350? It sounds like I need to start doing some fiddling.

--Thanks, chris
 

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TT
there are, or were, a couple of FCB bikes running 115's successfully. 110's are not crazy.
Are Alex's carbs marked with the same # on the side, or could they be a mixed pair. I think 3 or more versions all look the same from the outside but have different internal passages/jetting. Also, carb diaphrams have cracking or holes that are greater on one side? I had one set that was really mismatched, enough to throw it off, due to uneven cracking. Putting the same amount of liquid electrical tape on each helped balance it out.
 

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I am running 110's now and most of my competitors are running 115s here in the south on their 350GP bikes. This is with the stock runner air horns in place.
 

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115's are not out of the realm. rosko has a great sheet showing the various jetting combos for certain carb numbers. they do vary. im running 110's in mine and the plugs always look perfect.

jc
 

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Discussion Starter #17
I'm still at 105's with some minor adjustments to the needle and it's a huge improvement. Let's see how it performs during practice on Saturday AM, worst case scenario I will bump up to 110's. Either way I'm racing baby.... Joe seems like in June I wont be lacking power, so it's on baby!

Sotomoto
 
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