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Old December 23rd, 2018, 06:07 PM   #1
dodgerdad
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Uneven header pipe temperatures

My bike recently received a carb clean/tune, air mix adjustment, valve adjustment, new spark plugs, and new petcock. I'll be syncing the carbs next week but today I checked the header pipe temperature by hand (recommended by another board member) as the bike was beginning to warm up and I noticed the two pipe temperatures vary quite a bit, coming out of the heads.

Does this point to a need for a carb sync??
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Old December 23rd, 2018, 10:15 PM   #2
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I doubt ducatiman sent back your carbs not synced. Usually out-of-sync doesn't make that dramatic of difference that you can feel in headers. That's usually more commonly caused by dead spark plug or igniton-coil.

Do compression-test on warmed up engine. You may have some worn rings or valves on one side.
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Old December 24th, 2018, 06:31 AM   #3
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It means that for some reason, and there are many possibilities, the two cylinders are not doing equal work when the engine is cold.

Not disagreeing with Danno, but if you suspect the carbs might be out of sync, why not check that first? If they need a sync adjustment, then do it and check the pipe temperature again. That will accomplish two things:

1. The carbs will synced and not be the cause of future problems.

2. You will know if out of sync carbs are causing your current problems because if they are, after the sync the head pipes will warm up at the same rate.

Once you rule out carbs as the cause of the trouble, you can move on to one of the other possible causes of the uneven head pipe temperature.
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Old December 24th, 2018, 07:24 AM   #4
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I assure you the throttle plates are synched. However.....as I alluded to after viewing the start up video....and I'll repeat...during initial startup, sounds like one cylinder being favored over another.

Remember during the course of your other thread we found:

*high fuel level in RH carb

*defective petcock diaphragm. After replacing "Bike fired right up and ran much better."

*during the vid, it was pointed out initially the choke was NOT opened all the way during startup...and was being left on for too long. Could delay to shut it be fouling a plug? Thus causing the "running on 1" sound?

At this point, a verification of spark plug condition may be of benefit. Associate condition to the cold and hot cylinders...see if the cold side is black/wet/dark and the hot side is normal.

Re valve clearance:

"What I found is that all the valve clearances where a bit too tight"

All intake and exhaust valves were tight? ALL?
Kind of unlikely every valve to be tight...

And I must ask once again.....you are absolutely CERTAIN you adjusted the valves in correct crank/cam positions?

I wish you had deferred valve adjust until after carbs were serviced and put back on...
doing too much at once clouds things up.

Is the cold cylinder the RH side again?

Not trying to beat you up..DD...but as I've alluded, with multiple issues...something else at play here. There very well may be more.

If you were here...in one session...valve clearance doublecheck, followed by compression test, condition of spark and inspection of caps, wires, connectors, etc, synch with mercury manometer, pilot screw reset......thats where I'd venture, at least...

Kudos to @triplejim @jkv45 @DannoXYZ ...we're tryin' our best.

Process of elimination can be frustrating, long and difficult.
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Old December 24th, 2018, 07:36 AM   #5
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Thanks guys, I really appreciate the brain work. The "cold" cylinder is the left one.

I guess I'll pull the plugs and take a look at them. They were new when my saga began but who knows what condition they may be in now. I'll inspect them prior to syncing.

As for the valve clearances, I re-checked them yesterday and they are within spec.

If the plugs are fouled should I replace them then proceed to test run AND then sync (if necessary)?

Thanks again, guys.
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Old December 24th, 2018, 08:01 AM   #6
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i'd be interested if you could post a pic of plug condition if less than perfect (I suspect they will be)

Curious that the RH side was first problematic and now its the LH.

Oh, and a Merry Christmas to y'all.
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Old December 24th, 2018, 09:10 AM   #7
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Quote:
Originally Posted by ducatiman View Post
I assure you the throttle plates are synched. However.....as I alluded to after viewing the start up video....and I'll repeat...during initial startup, sounds like one cylinder being favored over another.
Sorry for my ignorance of your procedure, DM. I thought I remembered that you sugested a sync check, but I must be thinking of a different thread.

Yes, if sync isn't in question, then on to the next step in the diagnosis.

Quote:
Originally Posted by ducatiman
as I alluded to after viewing the start up video....and I'll repeat...during initial startup, sounds like one cylinder being favored over another.
Which dodgerdad verified with the head pipe temperature test.
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Old December 24th, 2018, 09:51 AM   #8
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OK, I'll pull the plugs as soon as I get a chance and post up a photo of them.

Merry Christmas!
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Old December 24th, 2018, 12:07 PM   #9
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Photo

Had a few minutes to sneak away and pull the plugs. Seem OK to me.
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Old December 24th, 2018, 07:35 PM   #10
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Do compression test
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Old December 25th, 2018, 07:08 AM   #11
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^ at this point, agreed.

Plugs show no "smoking gun", major evidence of overfueling

The "one cylinder" sound at startup in the vid still eludes us.
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Old December 25th, 2018, 04:02 PM   #12
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Manometer video

Quote:
Originally Posted by Triple Jim View Post
.
Quote:
Originally Posted by DannoXYZ View Post
.
Quote:
Originally Posted by ducatiman View Post
.
So I checked the gap and reinstalled the plugs. I swapped the coils since it's an easy way to rule them out. I then hooked up my carb sync tool.

I started up the bike and again, the left pipe was significantly cooler right away which ruled out the coils. Once the bike was warmed up I recorded this video. It shows how the carbs are not in sync at idle but apply any steady amount of throttle and then they line right up. Release the throttle and they fall out of sync at idle again.

What does this indicate? Is it normal for carbs to "sync up" under throttle only?

https://youtu.be/pkDyL2g0E9I

(FYI: I haven't touched the sync screw yet. I recorded this and stopped. I hope to get some feedback before I go monkeying around with the actual sync.)
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Old December 25th, 2018, 04:15 PM   #13
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indicates they are out of synch.....go for it, tweak to get them equal at idle
see if any improvement and progress from there.
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Old December 25th, 2018, 05:33 PM   #14
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Quote:
Originally Posted by dodgerdad View Post
What does this indicate? Is it normal for carbs to "sync up" under throttle only?

https://youtu.be/pkDyL2g0E9I

(FYI: I haven't touched the sync screw yet. I recorded this and stopped. I hope to get some feedback before I go monkeying around with the actual sync.)
That's normal for slightly out-of-sync carb; greatest difference is idle. Higher flow with greater resistance and vacuum makes difference insignificant. That engine in video has some other major trouble if it's only pulling 10in.Hg at idle.

Again, little amount off flow-rate due to sync, 5-10% max is not going to cause so dramatic difference in header temps that you can feel (did you use both hands at once? Then switched hands?).

Most likely you have some major difference in combustion issue:

- worn/broken clogged rings on one side
- worn/broken valves on one side
- ignition issues: plug wires, trigger wires to coil

1. Do compression test first.
2. Then we can investigate ignition

Do you have access to oscilloscope?

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Old December 26th, 2018, 08:31 AM   #15
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go get 'em @DannoXYZ , all yours
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Old December 26th, 2018, 08:49 AM   #16
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@DannoXYZ : I have no oscilloscope. I can borrow a compression tester from a local auto parts store that loans them out but I'd have to see if they offer them with a small enough adapter/fitting for the plug hole.

I plan to do the sync today and hope that works out. I'm going to skip the compression test because, practically speaking, if it does happens to have some valve/ring issues I'm not willing to dive in that deep nor shell out any money for the work. Thanks for the diagnostic tips, I truly appreciate all the help here from the forum members.
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Old December 26th, 2018, 12:30 PM   #17
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Did the sync this morning, and took it for a short spin afterwards. I rode mainly through small residential streets in order to get a lot of stop and go riding.

Idle was consistent while at a stop and when coming to a stop. Taking off was MUCH improved with no noticeable hesitation or need to blip the throttle.

I'll fire it up tomorrow, cold, and see how it starts up with the choke applied and I'll also check to see if the header pipe temperatures evened out.

So far so good...
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Old December 26th, 2018, 12:47 PM   #18
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A compression test will show an out of spec low pressure if any valve is not fully closing. This means a compression test is useful to check for things that are not major internal problems.
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Old December 27th, 2018, 03:42 PM   #19
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Compression test will also show clogged rings that's not sealing properly. Usually due to burnt oil deposits caused by using dino oil. If not too severe, a piston-soak along with a couple tanks with PEA-based fuel-cleaner will clean rings enough to seal properly.
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