FI Gurus - Uneven Vacuum Between TBs at higher rpms.

Blrfl said:

Sevens are the standard plug, and unless the bike spends all of its time on the highway, don't run anything colder (higher numbered).
What do you usually put in it?
--Mark
and
IGoFar - Cruise Control?

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The standard plug per NGK is a CR9EH. The CR8EH is the option "one step" hotter plug, and what was in the bike when I got it, and what went back into it early spring 2014. I was just going to try the 7s for a while and see what the result looks like. By cross-ref, the Denso U24FER9 is shown as "standard," and the x-ref says Denso 24 = NGK 8. I'm certain the NGK 7 is not the standard, and is a higher heat range than the 8s that are in it now.

I know the SM calls out a standard and an optional plug, but I don't recall the correspondence to the above - I'll look it up tonight. If I can get the problem resolved, I will probably run a set of the NGK Iridium-IX plugs in the 8 heat range for my 75% local/25% highway usage.
~~~

No automatic cruise control installed.

Thanks for all your help in trying to troubleshoot this unusual problem.

Randy

NGK plugs are hotter with lower numbers. An 8 is colder than a 7.

My '05 was delivered new with the 7s in it.

RandyIdaho said:

The standard plug per NGK is a CR9EH.

Click to expand...

NGK didn't design the bike and isn't the first supplier to have an error in its fitment guide. Here's a snippet from the 2008 owner's manual:



BTW, one of the causes of oil and carbon fouling is plugs that are too cold. Also check your air filter, because if it's obstructed on one side, that could cause the same thing.

--Mark

fwiw my 04 came with CR7EH9
7 is the heat the 9 on the end is the gap.

A CR9 would be too cold.

The 1st catalog I came across (german 2014-2015) is suspect, listing
2002-2004 st1300 Pan cr8eh9 cr8ehix-9 iridium
2002-up st1300 A pan cr7eh9 with no iridium equiv.

Their us .com site does incorrectly list the cr9eh9 in the online parts finder.

The UK site does correctly call out cr7eh9 (pan is listed under 1260cc engine size)

If tech support responds I'll post it here.

This is about as wonky as EBS brake catalog for the ST.

Contrary to popular opinion here, TB sync. is not just an idle issue. Like carbs, the idle circuit influences the mid range. It's not an on and off switch. Especially for MPG at cruise on the highway when the throttle is just cracked off idle.

There is an adjustment in the left to right linkage. Easy to find in the manual it's one of the do not adjust screws. When I do my TB sync. I always check vacuum with more throttle also. My left to right bank was off and I adjusted it in.

I know there is some effect at high vacuum levels since the air bypass thru the start valve is a significant fraction of the total air flow. Problem of the imbalance does not appear to be 1-3 versus 2-4, do the left right link adjustment of not likely to resolve it. The difference is not that large. I just got the valve clearances checked (OK) and will be starting out up to re adjust the start valve sync. If the off idle balance is within a few mm Hg of each other, I'll call it good, button it up. And ride out the rest of this season and see how it runs. Wish me luck...