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Air Leak?

4K views 38 replies 9 participants last post by  o1marc 
#1 ·
Greetings, I haven't post here in quite a while.

After restoring my '76 T140V, I started it up the first time. Other than cleaning them, I did not change the idle mixture or jet size on the carburetor, I left it like it was when I got the bike about 5 years ago, since it seemed to run okay back then the couple times I rode it before I tore it down. It had a 200 main jet, a 3.5 slide, 106 needle jet, needle set to middle position. It started on the first kick after sitting for 5 years!

It idled nicely. I took it for a ride. Ran okay, but seemed to blubber at high speeds. Checked the plugs when I got back in the garage. They were sooty black. I then discovered that the idle mixture screws were set less than 1/2 a turn out!

As per factory specs, I replaced the slide with a 3.0 and the main jet with a 190. I also installed a new 106 needle jet, left the needles in the mid position, backed the idle mixture out to 1.5 turns, then started it. It barely ran. When I screwed the idle mixture screws in, it smoothed out, but the engine raced. I backed the Idle adjustment all the way out, but it still idled high..about 2000 rpm's. Is this an air leak? I used new gaskets on the engine side of the manifold and new thin o rings on the carb side.
 
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#3 ·
The carbs have no chokes. I realize now that I over tightened the carbs on the o rings. They will flex slightly up and down, but not sideways.I will look at them today. I hope I didn't ruin the carbs. I will use the thicker o rings and just snug them up.

Is there a big advantage of using the thick spacer between the manifold and the cylinder head?



 
#4 ·
The thick fiber washers between the carbs and the head help lessen the heat transference from heads to carbs. (Helps not stops)

Here in FL the heat is bad enough. The fuel in the bowls can boil in traffic.

I've heard of some having to flood the carbs to help cool them down before it would crank up again.

Air cooled engines and Florida traffic are sometimes not very compatible.

(Sorry Occifer. I HAD to ride on the sidewalk to cool the engine!)

You have one of them there new fangled motorcycle machines so I don't know if they are supposed to have the thick gasket or not.

It can cause clearance issues with the filters. My timing side breather just barely clears with the thick gaskets.

Where ya at fellow Floridiot? :grin2:



ETA Ya missing a balance hose? I see a nekkid banjo stub.
 
#9 ·
Loxahatchee is kinda like Bradenton.

It USED to be a nice quiet place until someone started promoting tourism!

NOW everything costs too much and it's overrun with humanity! And traffic. And urban sprawl. And strip malls. (And strip clubs!)

My little Cow Town is too big for it's britches and when I retire I'm moving to the middle of the state to get me some boondocks! (And hide from hurricanes)

PLUS Polk county has some topography and nice back roads for mo-mo-ing in my old age. :grin2:
 
#10 ·
I kept moving further north from the city to get away from the rat race. Do it enough times and you find you are now on the south side of another rat race with nowhere to go. When I moved to Dawsonville 23 years ago we were way out in the boonies. Now traffic is just getting unbelievable and they are having to install the first "constant movement" intersections in the state. All my local passing zones are gone and there are traffic signal lights all over the freaking place now.
 
#11 ·
I just use a thick fibre gasket and not bother with an O ring.They dont move,leak air,or boil the petrol.There is also no chance of warping the flange when set on a flat fibre spacer.Some people persevere with an 0 ring and it works though.
 
#13 ·
Back out to the garage. I went ahead and put the spacer between the manifold and cylinder head, no gaskets. I used Hylomar. I also used the thicker o ring on the other side.



I also checked the timing thinking it might have moved. I am using a Tri Spark ignition and it was pretty much dead on. Approx 38 degrees BTDC, based on the timing mark anyway.

Started the bike.. ran like crap. Blued my new pipes! Running very lean.

I then decided to reinstall my old 3.5 slides. Although it would make the engine run even leaner, my logic was that it ran rich with them in there before. Also I noticed the 3.0 slides that I just installed were noisy when I turned the throttle with the bike not running. hmmm strange.. To my surprise, when removing them, I noticed the new 3.0's fit very loose.. I could rock them around side to side. I haven't owned a Triumph in years, and the seller stated that they would fit 928, 930 and 932 MM carbs. I guess not, unless my carbs have been modified(?) I didn't notice this when I installed them. I have Amal 30 mm carbs, verified by the reading the casting.


3.0 slides:



3.5 slides:



Side by side:



Once the 3.5's were back in, the bike ran much better. The slides also fit tight. I took it down the road, chopped the throttle and checked the plugs. Very lean. Took it slowly home and changed the main jet from 190 to 200. Took it out again. Better but still too lean.



Did a compression check. 170 on the left and about 155 on the right. Also, the the idle mixture screw affects the left cylinder, but on the right, it has no affect, even when screwed all the way in. I readjusted the valves. One exhaust valve was a little loose. Others checked correct.

Thinking maybe I should order the right 130 slides (?)

Where should I go from here?
 
#14 ·
The slides should not have play in them.That is the same as wear which allows air around the slides and leads to poor tickover.Once these slides have wear,it is not easy to get an even tickover at all.I have been using just a thick gasket on carbs for more years than i can remember with no problems at all.I also seal them with Blue Hylomar.
 
#18 · (Edited)
Apparently my carbs have been "resleeved" which is why the new throttle valves fit very loose. The ones that came with the bike have " Mike Gaylord Products" stamped on them. Is anyone familiar with the process? Where would I find a 3.0 throttle valve that would fit?

Edit:

After reading how much better the 930 Premier Carburetors are, i'm thinking about getting a set.

I noticed the banjo union only has one inlet. Does this have to be traded for the two inlet type that I currently have? Makes me think that my reserve will no longer work if I don't..
 
#15 ·
Clear your idle jet on a right cylinder poking it with suitable very thin drill or soft wire, spraying with carb cleaner.
I always check with carb cleaner sprayed in the threaded hole of the air screw if ( after dismantling top of the carb with slide and spring ) can get a cloud of cleaner going through small holes located under the slide.
If your needle jets are new and original Amal's part I would take the needles one position up from middle position.
 
#16 ·
Thanks guys for all the info. I just got the needles today and when I install them I will make sure the idle jet has a clear passage.I will also check for air leaks with WD 40 just to make sure.
 
#17 ·
See that steel bolt threaded into the bottom of your left side aluminum intake manifold?
Bet a buck the bolt isn't tight in the manifold threads until the engine is up to temperature.
I've had to seal mine twice in as many years to get smooth running before heat up.

Really dumb idea to mix metals in a sealed fitting.
 
#19 ·
Hi,
As Rambo mentioned earlier, loose fitting slides allow air to leak around the slides and into the intake. Usually shows as a high idle speed that is not affected by adjusting the idle speed screw. Sounds like those Premiers might be a good idea!
All the best,
Andy
 
#20 ·
Andy, You missed my point.. The old throttle valves in my carbs are 3.5's.. they fit nice and tight. They are made by Mike Gaylord Products.. apparently a company that re-sleeved carbs. I needed 3.0 throttle valves to run richer, so I ordered a stock Amal set. They were the wrong diameter, although they were new. I mean really loose..not like "worn loose". From the ebay ad, they were suppose to fit all 30MM carbs. So I assume when they resleeve a carb, they bore it out. I was asking about the process. Seems that in order for me to get a 3.0 throttle valve it would have to be a special one to fit my modified carb. I decided to just order a new set of carbs since I could find no info on resleeved carb parts and obtaining a 3.0 throttle that would fit my apparently modified carbs.
 
#22 ·
Story of my life:
I recently came up upon a stubborn wheel lock on our car. It was installed by hand so it shouldn't have been overly tight but it stripped the removal key.
Then I tried to pound a tight socket on it but rather than grip the lock when turned, it just took the chrome off the lock and rounded it off, getting stuck on the lock.
It took some time to grind and convince the socket off the lock, and then I was not even back to square one because the lock's surface was changed.
Then I sent away and paid for a replacement key......it stripped in moments just as easily as the original.
Next to research wheel lock removal tools.....looking at another $35 to $50 without guarantee the tools would do the job or even fit.
By then it had been a couple weeks of efforts.
While driving through town I happened to stop by the tire shop, just as a long shot......lock was off in 5 minutes....cost zero.

Since you've restored the bike, would a new set of carbs be out of the question?
It might save the cost of therapy down the road after all is said and done. (LOL)
 
#23 ·
About the gasket/O ring discussion, my '76 had overheating carb issues when I unwittingly defeated Triumph's design efforts.
A standard gasket at the head and the "proper" thick O rings at the carbs works just fine and suggest you not re-engineer the system.
Mine idled and ran perfectly in the past few weeks of 90+ degree days.

A problem you'll find messing with the gasket/insulator thicknesses is find proper stud lengths.
It's not worth correcting what they had right in the first place, atleast not for me.
 
#25 ·
With the thicker gaskets and o ring I had enough stud sticking out to hit the locking area on the nut, but it was close. What drives me crazy is torquing down the stud in the head. I tried using nuts, but then the stud backs out when I try to get the nut off.. only way I found to do it is to use a pair of vice grips on the smooth part of the shaft, but is scars it a little.
 
#32 ·
ChuckB,
There's no need to use "thicker" gaskets at the head for heat reasons if the proper O rings are used at the carbs.
Standard gaskets work fine.

As for mounting the studs, I often thought of grinding some thin grooved in the studs to allow the use of a thin wrench.
Otherwise it IS a PIA to get them to stay put on subsequent removals as you've noted.
 
#36 ·
I think you are right..By using the thicker o rings, a barrier is already created. I ordered a set of the thicker gaskets to go up against the heads, but I don't think I will use them.

Rethinking one of my previous posts, even If I used the thicker gasket, which I have decided against, it will not affect how much stud sticks out, only how much stud goes into the head.. :rolleyes:
 
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