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TR4/4A Sputtering when hot TR3 & TR4

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Re: Sputtering when hot TR3 & TR4

Richie - I changed all the rubber hoses to my carbs for new ones and I add 4 oz. of Lucas Gas Saver (Upper Cylinder Lubricant) every tankful. This is available at Cdn Tire. My last trouble was on the way to Bronte Creek British Car Day about three years ago with Petro-Can 94 in the tank. I got to Smith Falls and filled it up with 89 octane Esso. The rest of the trip was fine. On the QEW, I was driving smoothly at 90 MPH. It has run fine every time I use my TR. I no longer have any problems with 89 octane if I fill it with Shell or Esso. I stay away from Petro-Can and Sunoco like the plaque.

A few weeks ago at the Ottawa British Car show, a 12-year old Chinese Canadian started it with the hand crank on the first try. It idles nicely at 400 RPM. Even I can do it.
 
Re: Sputtering when hot TR3 & TR4

Wouldn't that extra foam on the air cleaners reduce the amount of air getting to the carbs just enough to sputter a car sitting in traffic on a hot day?
 
Re: Sputtering when hot TR3 & TR4

That hasn't been my experience. I made my koozies from a foam filter meant for a ShopVac. That stuff is designed to allow a lot of air to pass through but still catch some dust. If I pull off or put on the sleeve while the engine is idling I detect no change in idle.
 
Re: Sputtering when hot TR3 & TR4

The amount of restriction (ie drop in air pressure) across the filter is proportional to the air flow through it. If they are going to cause any problem at all, it will be at high rpm and wide open throttle.

Personally, I much prefer to run paper element filters from a later Triumph. The dust around here is very abrasive, and I don't trust the foam to stop all of it. Even ShopVac says to use a paper element under the foam, when working with dust.
 
Re: Sputtering when hot TR3 & TR4

Well, spring is around the corner and it dawned on me I never got this problem sorted out last season!

With multiple fill-ups of ethanol-free fuel I still experienced lots of problems as mentioned already in the thread - most notably after letting the car sit for 20-30m. The poor drivability and sputtering would last for a good 10-15m of driving, and was clearly related to how much air was moving through the compartment (ex: 10-15m of stop & go would only make things worse).

After re-reading the thread I caught post speaking to ensuring the vents on the float bowl covers were clear - however I'm pretty sure these vents were only added to the later models of carbs ?

I'm just trying to think of any final attempts I can try before spring - side of rebuilding the carbs - which I'm not terribly certain is related to the issue.

Thanks!
 
Re: Sputtering when hot TR3 & TR4

richie said:
After re-reading the thread I caught post speaking to ensuring the vents on the float bowl covers were clear - however I'm pretty sure these vents were only added to the later models of carbs ?
Click to expand...
All carburetors have some sort of float bowl vent. The later 'emissions' carbs actually had two of them, with a valve to select a different vent when the throttle was closed (so vapors would be routed to the carbon canister). Do you have SU HS6 or the ZS carbs?

On the Triumph version of the HS6, the vents are well hidden, but still there. I'm told that some of the Volvo HS6 carbs had a vent tube, but I haven't found any yet.

HS6bowlvent.jpg~original
 
Re: Sputtering when hot TR3 & TR4

TR3driver said:
All carburetors have some sort of float bowl vent. The later 'emissions' carbs actually had two of them, with a valve to select a different vent when the throttle was closed (so vapors would be routed to the carbon canister). Do you have SU HS6 or the ZS carbs?

On the Triumph version of the HS6, the vents are well hidden, but still there. I'm told that some of the Volvo HS6 carbs had a vent tube, but I haven't found any yet.
Click to expand...

I've got the original Strombergs!
 
Re: Sputtering when hot TR3 & TR4

Ah, both were used on 4A, so I didn't know. Unfortunately I'm not as familiar with the early ZS carbs, so someone else will have to illustrate where the vent is. Most likely through the face of the carb (into the air filter), but I don't know for sure.
 
Re: Sputtering when hot TR3 & TR4

If you have the ZS carbs I think you have, there will be 4 holes in the carbs' air box mounting flange.
2 will be threaded for the fasteners that hold the air box attached to the carb.
That leaves the other 2 as possible ports for venting the float chamber.
I believe it's the one on the left, but it's easy enough to check.
Lift the air valve so you can see inside the carb and using a soda straw or the like, blow into the hole.
If it's the vent, you'll see gas bubbling up thru the jet inside the carb.
But I don't believe that the symptoms you described fit for a blocked float chamber vent.
A blocked vent would inhibit the normal rate at which the float chambers fill with fuel.
After running for a while the engine would probably just start sputtering and possibly die from lack of adequate fuel.
 
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