Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesSRM EngineeringLucas Classic MotorcycleHepolite PistonsIndustrial tec supply

Upgrade your membership to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Welcome to BritBike Forum!
Britbike forum logo
Member Spotlight
Chip205
Chip205
Southeastern PA
Posts: 27
Joined: November 2004
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Previous Thread
Next Thread
Print Thread
Page 4 of 4 1 2 3 4
Joined: Nov 2008
Posts: 3,362
Likes: 37
D
Britbike forum member
Offline
Britbike forum member
D
Joined: Nov 2008
Posts: 3,362
Likes: 37
I saw that detail on the plugs. What's the advantage? I have found that Denso plugs cured a misfire at one point in a long ride, on one bike, and have been using them ever since.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Support Your #1 BritBike Forum!

Check out British motorcycles for sale: British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Joined: Nov 2012
Posts: 2,067
Likes: 59
K
Britbike forum member
Offline
Britbike forum member
K
Joined: Nov 2012
Posts: 2,067
Likes: 59
"How about this one, same bike but a harder run and cleaner shut off than above....Surprized you missed the clipped electrode NGK Competition plugs...The engine has Mikuni flatslides."

So what difference does it make? Doesn't heat affect it just the same?

Joined: Jan 2017
Posts: 1,561
Likes: 55
T
Britbike forum member
Offline
Britbike forum member
T
Joined: Jan 2017
Posts: 1,561
Likes: 55
Hi Allan, I like to mark in 1/8ths as there is a fair amount of overlap in my way of feeling carb. Main jet is simple. Needle clip, cutaway overlap. I try to gauge which way I want to go with this. Snap throttle is basic test for cutaway, but I find it overlaps into running on beginning of needle taper.

I find it gives me a better gauge of were slide is that 1/4s. Just a matter of personal preference I guess.

Mark it anyway you choose. However, you must know where slide is.
Don


1973 Tiger 750
Joined: Jan 2017
Posts: 1,561
Likes: 55
T
Britbike forum member
Offline
Britbike forum member
T
Joined: Jan 2017
Posts: 1,561
Likes: 55
Hi John, I did not misspeak on turning mixture screw out.

I cannot explain this. Why that helps. I've observed this on worn carbs several times now. Something odd happens making motor die at like .005" lift, maybe even less. The motor will flat die. Even riding rolling on throttle very slowly motor will die, but... momentum keeps it spinning & it restarts.

I've always thought it was lean, but mixture screw in makes it worse. Out makes it better. I don't get why. Should you get worn carb job through shop, heat soak it & see if you experience similar.

Does 91 E10 California fuel effect this? 100% of time so far. new carb(s) cured this 100%. No matter how slow you work throttle with new carb you can't make it die or even hesitate, it just keeps running smoothly & rpm increases ever so slowly.
Don


1973 Tiger 750
Joined: Oct 2003
Posts: 4,089
Likes: 9
D
Britbike forum member
Offline
Britbike forum member
D
Joined: Oct 2003
Posts: 4,089
Likes: 9
I didn't manage to leave the thread! My light plug is like Hillbilly's light one but the other is a fair bit darker. As John and others said said I think it must be wear on one side more than the other in my case.

Looking in the Triumph workshop Manual I saw that it does mention the bias between cylinders and says to tune the bike to get the left one correct. I think that if I did that the other would be v. hot as my dark one is the left..

John- when you mentioned valve seats did you mean leaking, sunken or both?

Dave

Last edited by dave jones; 03/27/21 8:43 am.
Joined: Oct 2012
Posts: 5,690
Likes: 119
knuckle head
Offline
knuckle head
Joined: Oct 2012
Posts: 5,690
Likes: 119
Originally Posted by koan58
"How about this one, same bike but a harder run and cleaner shut off than above....Surprized you missed the clipped electrode NGK Competition plugs...The engine has Mikuni flatslides."

So what difference does it make? Doesn't heat affect it just the same?
The plug in the photo is not too hot,it might be the photo or you like many others accept rich mixtures as normal. Refer to what JH says about chokes on cold engines,...Most don’t need them because of over rich mixtures....the AMAL Concentrics in good shape work as intended on a stock engine. But the on size fits all pilot jet can be a hinderance when tuning for different situations. And In 2021 I feel no need to piss fuel when using ticklers on carburetors costing near $200 each new...
The results always talk the truth,.the leaner mixtures carefully tuned for the way the bike is ridden give sharpest throttle response and more power. There’s no detonation, no holes in the pistons, no overheating....It works for me and I’m far from the smartest guy here, but not afraid to try different stuff...


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
Joined: Oct 2003
Posts: 4,089
Likes: 9
D
Britbike forum member
Offline
Britbike forum member
D
Joined: Oct 2003
Posts: 4,089
Likes: 9
You know your stuff, Hillbilly.

I read somewhere else as well that a white insulator but with a ring of grey at the base means maximum power. Also I read that setting the idle as weak as possible without spitting back saves a lot of fuel around town.

My bike is in that state where generally I use the "If it ain't broke don't fix it" although things aren't tip top. I like to discuss things on here just in case.

Dave

Joined: Mar 2005
Posts: 10,638
Likes: 64
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,638
Likes: 64
leaking

Joined: Oct 2012
Posts: 5,690
Likes: 119
knuckle head
Offline
knuckle head
Joined: Oct 2012
Posts: 5,690
Likes: 119
Originally Posted by dave jones
You know your stuff, Hillbilly.

I read somewhere else as well that a white insulator but with a ring of grey at the base means maximum power. Also I read that setting the idle as weak as possible without spitting back saves a lot of fuel around town.

My bike is in that state where generally I use the "If it ain't broke don't fix it" although things aren't tip top. I like to discuss things on here just in case.

Dave
I know a few things but actually I dislike engine work and tend to use proven shortcuts...hillbilly engineering....
I do listen to John Healy because he says what not to do based on experience...
my T140 with flatslides is jetted lean for low speeds. It needs the enricheners left on for a few moments even in warm weather....once warmed up it runs flawlessly with none of that cammy sounds so many Triumphs have when trolling along in second gear in town...
To run lean jetting you need to be in touch with the engine’s needs. None of that snapping the throttle open like a kid on a 2 stroke 125....Learn to roll it open with respect , the bike doesn’t accelerate any faster with wacking the twist open......


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
Joined: Mar 2005
Posts: 10,638
Likes: 64
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,638
Likes: 64
Quote
Something odd happens making motor die at like .005" lift, maybe even less. The motor will flat die.
This is the point where the idle carburetor is switching to the main carburetor. It is the point where the secondary transfer orifice changes from delivering air to the idle circuit to delivering fuel to the main carburetor. There are many things that can upset this sensitive transition. The secondary transfer port is the larger of the two, and under the slide, of the two holes either side of the back edge of the slide. For this to work it must be clean and the orifice sized. Also the pilot jet must be clean and the orifice sized.

Flat dying is a classic sign of a lean condition. I would start by making sure the secondary transfer port is clean and sized (.040"). To trick it place the tip of a finger in front of the slides cutaway; then place the tip of your finger on the slide and lightly push it back and see what happens. This could give you some clues

In most carburetors a mechanical operated pump (often called an accelerator pump) connected to the throtlle mechanism does the job of the secondary transfer port.

Joined: Jan 2017
Posts: 1,561
Likes: 55
T
Britbike forum member
Offline
Britbike forum member
T
Joined: Jan 2017
Posts: 1,561
Likes: 55
Hi John, I can assure you in every last case the worn carb was very carefully cleaned & full flow through both drillings as well as idle passages was verified 3 times. I will not spend $200 on carb due to clogged/dirty/partially blocked passage. Tune of carb was carefully road tested & set. Tune of bike, grounds, electrics, spark, air leaks, was verified perfect in every case over a period of road tests.

I agree 100% lean will cause dying. The leaning of mixture screw helps to a degree. Of course motor is not best idle mixture. This has puzzled me for some years now.

So if there is not a odd super rich (you see not puff of black smoke), then the additional air flowing through idle passage somehow effects the transfer such it helps to reduce they dying. Once carb is really worn bad, even that doesn't help. I find it most interesting why the air screw out farther helps.
.
Raising idle helps as expected, but to really help you have to get to 1150-1200+ even 1800 I've seen many do that. I don't know how they can ride like that as it's very inconvenient but they do.

I'm currently overhauling my motor & inspected slide/bore wear of my premier. I've observed almost zero wear in bore or slide after 10k miles. Original air filters from new with covers perfectly sealed to alloy boxes. Original wire/gauze elements.

The reason I like to whip dead horses is they can't run away. I'm too slow to chase the live ones!
Don

Last edited by TR7RVMan; 03/28/21 8:26 pm. Reason: changed sentence

1973 Tiger 750
Page 4 of 4 1 2 3 4

Moderated by  John Healy 

Link Copied to Clipboard
Job CycleBritish Cycle SupplyMorries PlaceKlempf British PartsPodtronicVintage MagazineBSA Unit SinglesBritBike SponsorBritish Tools & FastenersBritBike SponsorBritBike Sponsor






© 1996-2021 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5