Removing choke.

[Donut 77]

I suspect the choke is an area of vacuum leakage. I’m thinking of closing it off entirely. The bike will never be used in the cold months and at present it’s not needed and actually makes things worse when it’s pulled on. Not to mention the ball ache of getting it back together under the header tank etc.

My plan is to insert the needle/valve bit fully (closing the choke off), then put in the black plastic threads and fill the hole with high temp silicone. At least I can then say this is one less vacuum leak.

Anyone got any thoughts on why this might be a very bad idea?

[sirch345]

Although I understand your way of thinking, if it were me I wouldn't do that. You may find once you get your carbs back up to scratch you need the chokes.

My bike needs the chokes to start it,

Chris,

[freeridenick]

I agree with Chris. I kept the choke when I was using my bike on track days and races. I can't see the choke as part of your fueling issues. Fix those first and then see about the choke.

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[RodneyT]

Yep, I agree about leaving the chokes as is. Even in sunny Darwin (30ºC most days) I need a bit of choke to get my VTR started.

[Donut 77]

I thought I’d try it anyway, as they are spare parts and I’m now perfecting the art of getting the carbs off and they had to come off again tomorrow anyway. Nothing ventured and all that..

Verdict so far is that you were all correct. Even though I never used choke before and it was always fully closed, there must be a tiny bit of bypass air that goes through that circuit anyway. With it sealed off (as in below pic) it doesn’t like it one bit - even on a warm start, although a tiny bit of throttle compensates.

My initial idea was that as it’s always closed and there’s a possible air leak, why have it? I still haven’t answered that yet.

It’s all valuable learning though..

Choke is going back on tonight

[sirch345]

I thought I’d try it anyway, as they are spare parts and I’m now perfecting the art of getting the carbs off and they had to come off again tomorrow anyway. Nothing ventured and all that..

Verdict so far is that you were all correct. Even though I never used choke before and it was always fully closed, there must be a tiny bit of bypass air that goes through that circuit anyway. With it sealed off (as in below pic) it doesn’t like it one bit - even on a warm start, although a tiny bit of throttle compensates.

My initial idea was that as it’s always closed and there’s a possible air leak, why have it? I still haven’t answered that yet.

It’s all valuable learning though..

Choke is going back on tonight

Well that's one way to find out if sealing the chokes off works

Looking on the bright side you now at least know the answer first-hand

I'm not sure who's going to be able to answer your question though

Chris.

[Donut 77]

Right, so the choke went back on.

Starts much better. The flutter when you blip at tick over has also gone, so I’m happy that this was likely from a vacuum leak before I tightened up the carb rubbers.

I had also switched from 45 to 48 pilots, and the engine revs nicely.

The new symptom is this tick tick sound.

Does anyone recognise this as a classic symptom of too lean/rich.

Thanks for any help..

[freeridenick]

Right, so the choke went back on.

Starts much better. The flutter when you blip at tick over has also gone, so I’m happy that this was likely from a vacuum leak before I tightened up the carb rubbers.

I had also switched from 45 to 48 pilots, and the engine revs nicely.

The new symptom is this tick tick sound.

Does anyone recognise this as a classic symptom of too lean/rich.

Thanks for any help..

Sounds like carb farts to me. Did you balance the carbs and check the TPS? That usually sorts it.

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[sirch345]

Right, so the choke went back on.

Starts much better. The flutter when you blip at tick over has also gone, so I’m happy that this was likely from a vacuum leak before I tightened up the carb rubbers.

I had also switched from 45 to 48 pilots, and the engine revs nicely.

The new symptom is this tick tick sound.

Does anyone recognise this as a classic symptom of too lean/rich.

Thanks for any help..

Great to hear you have made good progress for most things with the carbs

I'm not sure what that odd noise is though
Try what Nick suggested if not already done, other than that hopefully someone else will have an idea

Chris.

[Donut 77]

Hi, the tps still had the factory non adjustable bolts. I did check it anyway and it measured I think 550 so I thought that was close enough?

I haven’t balanced the carbs yet this time because I’m struggling with tuning the pilot screw. On the rare occasions when I can get a positive connection on these screws, I can’t find peak revs. Feel like I’m pissing in the wind a little bit. This is what lead me to the vacuum Leak to begin with.

I’m fine with balancing them, but the pilots are still a dark magic that I haven’t mastered.. that’s one of the reason I post videos, in the hope that someone might diagnose lean or rich, then I can at least turn the appropriate direction and test them at a new setting. I appreciate this isn’t very scientific though.

I changed to 48 pilots and they are set at 1.5F 1.75R in this vid.

We are heading out for some long rides this weekend. I think from previous suggestions, it will be the best way to run tests and clear it’s throat after much tinkering..

[Donut 77]

Fingers crossed all sorted.

In the end, I gave up on trying to find peak revs and just left the pilots at 1.5F 1.75R in an effort to get towards balancing. I know this might not be perfect, but it’s in the middle of the range 1-3. Bike seems happy at this.

Then I balanced, which was interesting, as it was way out. I assume was the cause of the farts (thanks for advice on that Nick) It took a while because the manometer fluid would balance at tick over, but change at higher revs, or vice versa. I’m guessing that’s because with the bike stationary, the 172 rear main jet compared to the 170 front gives a bit more vacuum with revs. As a compromise, we got it sweet around 3k rpm.

Anyway, ticking/farting has gone. It rides the best it has done yet, ready for our weekend in the saddle..

The manometer was 2 washing powder bottles from B & M stores glued together - £1.50 each. Easy to drill air tight seals in the cork stoppers.

[freeridenick]

Great news. If you didn't recheck your TPS after balancing it's worth doing it. Generally balancing ends up with a change to the idle screw setting, which has a knock-on effect on the TPS. I'm not aware of any carbs that don't have adjustment. I thought all the TPSs we're slotted. The bolts might be Torx with a nib in the middle. That's irritating but the Torx sockets are available to match.

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[Donut 77]

I have a pair of the security Torx bolts (holes in) in the TPS on a spare set of carbs. The ones that are in the bike are what I think they call ‘sheer bolts’, set from factory and have to be ground off. There’s nothing to adjust..

I will swap them on further tuning. I have read several people say that they’ve forgotten to connect TPS and it made little or no difference?

The idle screw definitely did need adjusting.

[sirch345]

Great news to hear that balancing the carbs has sorted that odd noise
Good call Nick

I like your Manometer

I don't think altering your TPS setting is going to make a lot of difference seeing as it's at 550ohms already.
I have mine set at 570ohms after I had it at 500ohms. I followed the advice from this link below. The bike definitely feels perkier at the 570 setting:
https://www.vtr1000.org/phpBB3/viewtopi ... 46#p494546

Chris.

[sirch345]

Hi, the tps still had the factory non adjustable bolts. I did check it anyway and it measured I think 550 so I thought that was close enough?

I haven’t balanced the carbs yet this time because I’m struggling with tuning the pilot screw. On the rare occasions when I can get a positive connection on these screws, I can’t find peak revs. Feel like I’m pissing in the wind a little bit. This is what lead me to the vacuum Leak to begin with.

I’m fine with balancing them, but the pilots are still a dark magic that I haven’t mastered.. that’s one of the reason I post videos, in the hope that someone might diagnose lean or rich, then I can at least turn the appropriate direction and test them at a new setting. I appreciate this isn’t very scientific though.

I changed to 48 pilots and they are set at 1.5F 1.75R in this vid.

We are heading out for some long rides this weekend. I think from previous suggestions, it will be the best way to run tests and clear it’s throat after much tinkering..

Enjoy your ride,

Chris.