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Sooting of spark plugs - carb related?

Old 07-09-2012, 02:19 AM
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Sooting of spark plugs - carb related?

Hello SH/Firestorm owners.

I thought I'd post this question here because there's a lot of tech know-how on this forum (And also because it's a nice story LOL).

I've had some issues with my current VTR1000f that I bought in the summer of last year. The cause of this became quite clear. There must have been a mouse in the previous owners garage that found the airbox of the VTR quite a nice home during the winter and used it as a home and storage place for seeds, peanuts, etc.

Unfortunately some of this also passed trough the old air filter, and got into the carbs. All this caused problems like really bad fuel economy (sub 25mpg-ish) and stalling.

After parting out the carbs and cleaning them I did the following:
- Returned the pilot's to stock #45
- Removed the shim from the stock needles (this is a tip that I found. If I ever get a lean running condition I'll return them but I'm quite sure I don't have that now).

(I live in the Netherlands, petrol cost almost 8$/gallon (converted) here so trying to make the VTR a bit more fuel efficient while you are at it makes some sense, I do use it for going from A to B from time to time.)

My VTR (still) has stock exhausts. The only thing that is different is the pilot screws are non-standard. They have are suited for flat head screwdrivers.

Now my problem: I've thouroughly cleaned the carbs, using compressed air on all the air channels. I've tried a lot of settings with the pilot screws. However I keep getting my spark plugs sooted in no-time. Real thick carbon off-set on them, and even some carbon off-set on the inside of the carburators. I'm looking at some possible causes? Any of this sound familiar?

What I can think of now:

- Spark plug voltage too low
- Obstruction built up in the exhaust
- Choke obstruction
- Still something in the carbs?

I'm looking for the most obvious causes for such a problem to remain. As I've had my motorcycle a part quite a number of times now and am getting a little tired of this.
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Old 07-09-2012, 02:37 AM
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Have you a clean new airfilter? (Original Honda or aftermarket cleanable)

Is the Airbox standard or did the mouse chew any holes into the plastic to gain access?

When you had the carbs off to clean them, was the choke working okay and not sticking on.


Might be an idea to buy a second-hand set of standard carbs and replace yours to see if that helps.

http://www.ebay.co.uk/itm/HONDA-VTR-...#ht_500wt_1411

http://www.ebay.co.uk/itm/Honda-Fire...#ht_500wt_1178

http://www.ebay.co.uk/itm/HONDA-VTR1...#ht_500wt_1178

Last edited by Wicky; 07-09-2012 at 02:54 AM.
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Old 07-09-2012, 03:14 AM
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Thx, @wicky,

The airbox if fine.

I couldn't detect any visible defects on the carbs. And I've actually had them a part 2 times. So my reasoning now is becoming that it might be something else. Going to postpone replacing them for now.
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Old 07-15-2012, 07:53 AM
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One other question. As stated in the start post the airfilter has been restricted. This has been for quite some time. After I bought the bike I first looked for other things so I think it got 2000 miles or so of running with an heavily restricted air filter. Could it be that this caused soot build-up elsewhere i.e. in the inlet channels or the exhaust. Or do these systems have enough flow as to not cause a restriction by soot?
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Old 07-15-2012, 08:25 AM
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A dirty air filter will cause the spark plugs to foul. You have not stated if the filter has been replaced. Judging by your wording it seems like you still have a dirty filter in the air box.

It is my understanding that only the USA models have a D shaped pilot screw head. Since your bike is in Europe, those slot head screws could very well be original equipment.
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Old 07-15-2012, 09:00 AM
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Ok, so if the screws would be original it would not be normal that the engine runs idle without stalling with the screws 1.25 turned out I suppose (#45 pilots)? Then an restriction elsewhere (not in the intake) could be likely?

Yes, I have replaced the filter. I would not be posting this question here if I had not done the obvious first.

Last edited by MrC; 07-15-2012 at 09:03 AM.
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