Putting this VTR back on the road.

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tony.mon
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Re: Putting this VTR back on the road.

Post by tony.mon »

Suggest that you borrow or buy a spare set of carbs, and fit them.
That's the quickest way to find out if it's carbs or something else.
If it's something else, it'll be either vacuum leaks or ignition/coils/plugs. Swap out each in turn to eliminate them.
You'll get there in the end.
It's not falling off, it's an upgrade opportunity.

jdugen
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Joined: Fri Aug 19, 2011 6:44 am

Re: Putting this VTR back on the road.

Post by jdugen »

Right, short of any definitive answer, I'll document where I'm at.
Just to appease the Gods, I stripped and blew through the carbs with compressed air, again. Double checking the rubber boots there was a shaving off the top edge of the rear boot, I must have caught it whilst fitting the carb bank. I did try to fit carbs individually by disconnecting the side plates, but this just results in bits comong loose when trying to refit (so dont waste time trying it).
With this cleaned up and using a flat blade screwdriver on the rear boot, the carb can be eased in with no damage. (A hot air gun is handy here).
A test run gave exactly the same symtoms.
I have tried blanking off the Air Control Valve, no difference. I even blocked off both choke elements just to be sure, No difference.

Much to the annoyance of the locals, I ran it up the rev range with the airbox out of the way. As it approached the 3K area, I noticed that the throttle slide began to vibrate quite significantly, higher and lower revs, the slide stayed pretty stable, lifting smoothly. As both slides do it, and, I know for a fact that the diaphrams are good and fitted correctly, I can only surmise that this is a frequency problem. That particular engine speed must just beat the slides spring tension. As this is exactly the the throttle opening that is giving me grief I will have to do some more investigating.

I have now raised the needles with a small washer as per various posts to alleviate any lean running in this area and have ordered some 48 pilot jets, to be fitted if no improvement.

A bit of a Eurika moment. The raised needles have almost completely eliminated the lurch, steady state throttle is so much smoother, its a different bike. However, today is cold and wet (of course) so I am waiting for a good run and the engine at hotter temps before congratulating myself.
I will be fitting the 48 jets as soon as they arrive and am now pretty confident that this will fill in whats left of the obvious VERY weak running just off the throttle stop.

My conclusion is that, as is known, these come setup on the weak side for environmental testing. As the miles tot up (33000 on this one) rubber does not seal as well allowing the marginal fuelling to reach critical lean conditions. It might be worth replacing the slide spring too as this must start losing some tension as the miles advance. I know from past experience that blow-by gases can start to affect carburation, though this runs clean there will inevitably be larger element of gases in the airbox, reducing the mixture purity.
Once again, ALL I have changed is the needle height and this has given an immediate and positive improvement.
Stay tuned for any further developments.

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AMCQ46
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Re: Putting this VTR back on the road.

Post by AMCQ46 »

I can confirm that the throttle slides on my bike also flutter at about 3 or 4,000 rpm with no load, so that sounds normal.

I cant remember if you said the bike had been laid up for a while, if it has, then there may be more blocking the jets than you can clear with an airline. I have found on old bikes that old fuel can block the jets almost like a hard lacquer, and to get rid of this I resort to 2 tricks.
1) seriously heat the jets with a blow torch to burn off the lacquer, then blast through again with airline [make sure jet has cooled down!]
2) physicaly clean the jet with a strand of copper wire, this is the last resourt as the brass jet is soft and stricking a wire into it can increase the size of the hole........hence you need to use the softest material you can dont use a drill or anything steel
AMcQ

jdugen
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Joined: Fri Aug 19, 2011 6:44 am

Re: Putting this VTR back on the road.

Post by jdugen »

Hi
Ooops, I did post a reply but its either gone into the ether or I (more likely) didnt press submit... Old age..
Right, to clarify, yes, this has been standing for at least five years. Worse, though, the tank was half full of stuff that smelt like wood floor sealer, but was old petrol. The tank was thoroughly flushed of course, but I am thinking that the carbs will have sat with the same stuff in them. I know that CV carbs have lots of galleries drilled into the bodies and that its more than likely one of these is gummed up with laquer. I'm pretty sure now that I am masking the problem by richening the mixture, but, as it now runs acceptably it will let me put a few tankfulls through it, that usually starts to clean things up. I would spring for some replacement carbs, but there is no gaurantee that they will be any better.
Just waiting for the 48 pilot jets to arrive and I will update when they have been fitted.

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Flatline
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Re: Putting this VTR back on the road.

Post by Flatline »

Clinty is breaking a vtr it on here and ebay

Item 130578838140

He will have some carbs, any good?

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AMCQ46
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Location: Worcestershire / Warwickshire border

Re: Putting this VTR back on the road.

Post by AMCQ46 »

jdugen wrote:Hi
Ooops, I did post a reply but its either gone into the ether or I (more likely) didnt press submit... Old age..
Right, to clarify, yes, this has been standing for at least five years. Worse, though, the tank was half full of stuff that smelt like wood floor sealer, but was old petrol. The tank was thoroughly flushed of course, but I am thinking that the carbs will have sat with the same stuff in them. I know that CV carbs have lots of galleries drilled into the bodies and that its more than likely one of these is gummed up with laquer. I'm pretty sure now that I am masking the problem by richening the mixture, but, as it now runs acceptably it will let me put a few tankfulls through it, that usually starts to clean things up. I would spring for some replacement carbs, but there is no gaurantee that they will be any better.
Just waiting for the 48 pilot jets to arrive and I will update when they have been fitted.
yes, when petrol goes stale it stinks! so there is a risk that the jets are gummed up with lacquer, but sounds like you know what you are doing.

One other comment is that it may be worth giving the tank a big clean out using old nuts & bolts, or medium gravel to dislodge the sh1t & corrosion that might be in there..........Also fit an inline filter on both carb feeds to make sure nothing is getting into teh float boals that may block the jets again
AMcQ

jdugen
Posts: 35
Joined: Fri Aug 19, 2011 6:44 am

Re: Putting this VTR back on the road.

Post by jdugen »

Bit of an update
48 pilot jets arrived today, fitted this morning (I can do this blindfolded now).
There has been a dramatic improvement in slow speed runnig, the enormous backfires into the airbox have stopped entirely, it is now a pleasure to potter around at town speeds. I still get the odd clutch grab episode from stop to keep me on my toes, but that problem seems to have abated. I was running the airscrew at 3 turns out on the standard 45's, I put them back to a more reasonable 2 out on the 48's.
Now I can get it out, I took it for a longish run on the motorway, as much to get some fuel through it as anything else.
Giving it some hard throttle, it performs well (all gears, up to go to jail speed), but backing off into criuse mode, the lurching is still there. It also has a dead half second when cracking the throttle open again. But, as soon as I calmed it down and stuck to a steady 60 mph, it smoothed out and ran perfectly.
I've done the usual, fuel flow is good right through to the carbs, no airlock in the tank, no pipe blockages, floats are good, (there is no adjustment tang on these so I have to take the fuel level in the floats as a given).
The accepted lore is that this is lean mixture surge and that the pilot settings are very influential. As it is impossible to get to the airscrew in situ (unless anyone knows a way?) I have gone back to 3 turns out AND have sealed the mixture screw to eliminate any airleak past the airscrew threads. (Most other pilot screws have a rubber washer on the body to create an airtight seal, I'm wondering wether this should have one?)
Time for a bath and a few beers, its ready for a test first thing tommorrow, unless any gurus can think of something else.

Cheers from a guy pulling out whats left of his hair.

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vtryorks
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Re: Putting this VTR back on the road.

Post by vtryorks »

Are the emulsion tubes perfectly round?

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stormingjoe
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Re: Putting this VTR back on the road.

Post by stormingjoe »

3 turns out seems excessive, when I bought my bike it had 1 turn out mine are now set at 11/4 turn out with bigger jets.
1998 Firestorm, 47,000 miles, forks valved & sprung, proflex shock +4mm over standard, manual ccts', k&n, 50#slow 185#/190# mains, front carb slide mod, R6 throttle tube, Tank raised, Viper cans, Coerce fork brace, EBC lite front discs & pads.

jdugen
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Joined: Fri Aug 19, 2011 6:44 am

Re: Putting this VTR back on the road.

Post by jdugen »

The Firestorm is FIXED!!!!!!!

A Mea Culpa incident, I'm ashamed to admit, BUT, a lesson for anyone having similar problems.
This one came to me as a chassis with fairings etc. loosley fitted, the front cyl had dropped two valves so it was head off and that lot replaced. A big cadboard box came with it that held brackets and some plastic panels, amongst which was trianglar shaped black plastic tray. With all the checks to do and a fuel tank full of goo the very first thng I did was to clean it, and remove the carbs for their day in the carb cleaner bath. Along the way I found a broken choke fitting on the rear cylinder (which I have blanked off) and a few hoses loose.
With all that made good I have proceeded to do all the tests as in the previous posts. Seemingly, no matter what I did, the damn thing had a steady state throttle lurch that would not improve, no matter what I did to mixture settings.
Here I have to cite previous experience. My Fireblade had a very awkward cover at the front of the frame which, as any 'blade owner will tell you, makes plug changes almost impossible. It is accepted that this can be removed to make engine access 'easier' with no detriments to running at all. Maybe you can see where this is going?
That triangular black plastic tray that I had ignored for the last week suddenly leapt into my mind. Something was upsetting the fuelling,,,,, I wonder if it is air turbulence? Sure enough, that piece of cheap black plastic would appear to be VITAL to smooth running at speed. Now I know what is happening I can see that the airbox snorkel would sit right in the airflow from under the fairing nose, the faster you go, the more turbulent the airflow, the more erratic the fuelling.
The lesson for today is NEVER run without that baffle, sometimes Honda do know best!

Thanks to the kind souls who have given some good advice along the way, I can only hold my hands up on this one. I got so fixated on the carbs that I didnt take in the whole picture, another lesson learnt the hard way.
Last edited by jdugen on Sat Sep 24, 2011 8:54 am, edited 1 time in total.

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AMCQ46
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Re: Putting this VTR back on the road.

Post by AMCQ46 »

Good info would never have thought about that option. Your work may help someone in the future :thumbup:
AMcQ

jdugen
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Re: Putting this VTR back on the road.

Post by jdugen »

Finally had my day in the sun.
Took her out for a run up to the North York moors. I ride with Miguel on his RS Sprint, a good, steady rder on a well sorted machine. If I can pull a gap on Mig then the bike I'm on is doing alright.
It did take some time to get used to the instant punch, roundabouts where a bit of a struggle, to much for 1st gear, too lumpy in second, in fact, it seems to hate doing circa 30mph. Apart from slow traffic running, it is now a very happy bunny. High speed cruising (now a smooth and relentless experience) is also a bit of a niggle. Its happiest in 5th gear at 80 (or so) mph, 6th seems to put it into the lumpy sub 4k rpm rev range, it could do with a larger rear sproket. But, that would make first gear an instant wheelie ratio,,, compomises, compromises.
It was all very good fun... until the fuel light came on ten miles from home! Mig, with his near 200 mile tank range, shook his head and smirked, as he pointedly said, no matter what the gap I pull, on an average ride he would be home a long time before me if I had to refuel so often.
Still and all, for all its little 'niggles' it is a good solid ride and seems to get aproval from the motorcycle masses. Very few 'storms around, I was the only one at a packed Devils Bridge, could be a coming cult machine....

jdugen
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Re: Putting this VTR back on the road.

Post by jdugen »

One more report. I'm now into the fine tuning endgame, little hiccups at town speeds tuned out now I have access to the airscrew (remove expansion tank bottle). I read in a post that removing the airbox snorkel gives some performance enhancement.. No, it dosent!!! I merely re-introduces the 'lurch'!!! Mess with the airbox at your peril.

Chiefy21
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Re: Putting this VTR back on the road.

Post by Chiefy21 »

Could you post a pic of this triangular piece of plastic please? I want to check it is on mine (I experience some hunting on a steady throttle also)!!
Thanks

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MacV2
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Re: Putting this VTR back on the road.

Post by MacV2 »

Chiefy21 wrote:
Mon Jun 29, 2020 9:23 pm
Could you post a pic of this triangular piece of plastic please? I want to check it is on mine (I experience some hunting on a steady throttle also)!!
Thanks
Having re read the posts it would seem he is talking about the heat sheild that fits in front of the carbs... Triangel is a bit of a misleading discription... :lol:

No. 1 the heat sheild.

https://www.ronayers.com/oemparts/a/hon ... 327a/frame

https://www.ebay.co.uk/itm/1998-Honda-V ... SwUxFezbEo


Lift your tank, you will see if its there or not, if fact you dont even need to lift the tank to see if it's in place. Just have a look at the right hand side of the bike in the headstock area & you shold see a plastic wall it will have what looks like a crude round hole cut in it, thats normal...
Lowering the tone since 2007...

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