New Amels Running Too Rich

LannyDaise

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Lanny
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1976 750 Bonniville
My 1976 750 Bonneville is running so rich I’m fouling spark plugs after five-miles. I’ve been using Champion N3C plugs, and I just installed new Amel’s and still runs rich. I live at sea level, and have adjusted the air screw up to two full turns before it starts boggling gown. Could this be a valve issue?
I have installed electric ignition as well.
Do I possibly need a different heat range of spark plug?
Thanks,
Lanny
 

speedrattle

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hi lanny

the N3C champions are the correct heat range for your bike.

you say you have new carbs. why did you buy them?

what are the needle jet numbers, main jet numbers, needle clip position, and carburetor venturi size in mm for your new carbs? if you bought carbs for your machine with tbe standard settings then it should be close to correct.

the standard settings for standard conditions are well-known, but perhaps you have something different.
 
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LannyDaise

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Riding for 50 Years
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Lanny
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1976 750 Bonniville
hi lanny

the N3C champions are the correct heat range for your bike.

you say you have new carbs. why did you buy them?

what are the needle jet numbers, main jet numbers, needle clip position, and carburetor venturi size in mm for your new carbs? if you bought carbs for your machine with tbe standard settings then it should be close to correct.

the standard settings for standard conditions are well-known, but perhaps you have something different.
Thanks for your reply. I’ll try to answer your questions and see if we can come up with some solutions…I’ve been fighting this issue for quite sometime, and the parts supplier recommended, with such old orginal carbs, I should just replace them. So, without taking them off and pulling them apart, I don’t have the needle jet numbers or Venturi size, but the needle clip position is on the middle position. I’ve thought about trying to move them…do you think I should try that?
I had a bad electrical short which fried my harness, and just completed a total rewiring and the only change I made was to complete the electronic ignition package, but this issue was giving me a problem before the harness problem.
Thank you for your thoughts,
Lanny
 

speedrattle

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the idle circuit shouldnt be fouling out your plugs if youre out on the highway. do they foul at highway speeds or just plonking around slowly? that would give you a clue. you can try dropping the needle to see if it has any effect.

your carbs should have a 930 stamped on the outside, if theyre original spec 30mm.

but assuming the carbs are reasonable the only things left to foul a plug are very high levels of soot from a misfire, and oil.

you said you had the problem prior to putting in the EI. what EI are you now using? what coils?

if the ignition is okay, are the plugs oily? what is the compression reading on the motor? oil on the plugs will look just like what you would think-- wet, black, and oily.

while youre thinking, you might try a different brand of plug in the same heat range. the new NGK resistor interchange for Champion N3 is NGKBR8ES, i think.
 

LannyDaise

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the idle circuit shouldnt be fouling out your plugs if youre out on the highway. do they foul at highway speeds or just plonking around slowly? that would give you a clue. you can try dropping the needle to see if it has any effect.

your carbs should have a 930 stamped on the outside, if theyre original spec 30mm.

but assuming the carbs are reasonable the only things left to foul a plug are very high levels of soot from a misfire, and oil.

you said you had the problem prior to putting in the EI. what EI are you now using? what coils?

if the ignition is okay, are the plugs oily? what is the compression reading on the motor? oil on the plugs will look just like what you would think-- wet, black, and oily.

while youre thinking, you might try a different brand of plug in the same heat range. the new NGK resistor interchange for Champion N3 is NGKBR8ES, i think.
Aloha Speedrattle:
Thank you for the input, and I apologize for the tardy reply, but I wanted to try those spark plugs you recommended. Being on Maui, of course we almost have to order everything, but they came in and I’ve had a couple of good rides to help evaluate some things.

I believe you’ve sent me on a tack that I wasn’t considering, as I’ve been so focused on trying to lean-out the carbs. You brought up soot & oil seeping, and by-dam the left side plug is oily, and the right side still looks to be too rich. These plugs haven’t fouled yet, where the Champions may not have gotten me home from these two rides!

I don’t have a compression gauge, but it still takes a good kick to get her to turnover. I’ve noticed the leftside Is smoking a bit whiter than the less-noticeable darker smoke on the right side. Those new Amal’s are stamped 930, and I have the air adjustment screw out one & three-quarters turns. When I try to open them more the engine begins to labor. When I get us up to 3,500 rpm, she seems to be running a bit tight, so I feel there is something holding me back on the higher rpm range.

I’ll have to lookup what kind of EI I put on, but that was long time before my harness issue. I wanted to get this to you now that I’ve ruled that these plugs are better, and that I need to look into the oil issue. I guess I’ll drop that needle a notch and see if that helps.

I really appreciate your help…I’m having figure this out on my own over here.

Lanny
 

speedrattle

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well, theres only the three ways to foul a plug: ignition misfire, rich fuel, or oil deposits. you might have two or all three.

i switched from champions to NGK years ago because of fouling problems. the NGKs work for me. if the BR8ES works better, then thats a step in the rightvdirection. you can testvthe spark with an ordinary strobe timing light. hook it up pull the trigger, and look for a steady flash. run the rpms up and see if it is still steady. if theres more than about 12 percent misfire, somrthing is not right (on new plugs).

your new carbs may have been sold with generic jetting, which will always be too rich. or they may have been set up with the factory settings by the people who sold em to you, in which case they oughtbto be close. you csn ask them, or take the bowls off and unscrew yhe main jet holder to see the numbers on themain and needle jet. the service manuals have the stock numbrrs and they are all available on line for free.

what are your chokes set at? you should rotate the lever CCW to richen the mixture for starting, and then gradually pull the wire tighter as the motor wsrms by rotating the lever CW until its at its stops. look into the carb mouth and make sure the choke slides are actually going up.

on the oil, if thats what it is its from rings or valve guides, and either is more than just a tuning fix. so check for steady spark and double check those chokes.
 

speedrattle

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btw

. I’ve noticed the leftside Is smoking a bit whiter

the whitish smoke is typical of oil burning. if theres enough burning to make smoke, you may not be able to solve this problem without attention to the motors top end.

. . . than the less-noticeable darker smoke on the right side. Those new Amal’s are stamped 930, and I have the air adjustment screw out one & three-quarters turns.

darker smoke is typically fuel. that setting for the idle air screw is typical for a correct idle setting. it should not smoke at that idle air setting unless something else is wrong.

When I try to open them more the engine begins to labor. When I get us up to 3,500 rpm, she seems to be running a bit tight, so I feel there is something holding me back on the higher rpm range.

by "labour," do you mean that the motor will not accept throttle cleanly below 3500 or that the problem occurs from that rpm on? severe richness will cause tbe motor to misfire everyother stroke, called "eight-stroking," or "blubbering," or "motorboating."

what do you mean by "running tight?"

does this labouring problem occur at all throttle positions or just one? you can mark your throttle with tape and a pen to test. a carburation problem will be associated with throttle position, while something that occurs at a specific rpm tends to be ignition.
 
Last edited:

LannyDaise

Member
Riding for 50 Years
Local time
Yesterday, 17:35
Joined
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Messages
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Age
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Location
Maui
First Name
Lanny
My Ride
1976 750 Bonniville
I’d really like to thank all of you who helped me with my challenges! These last two-weeks, she is running & looking so fine! I would not be enjoying her again, without all of your help!
Mahalo nui loa,
Lanny
6AA52300-92BF-48D7-B62F-33644110793E.jpeg
 

speedrattle

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Riding for 245 Years
Local time
Yesterday, 23:35
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kevin
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T120
good to hear thst youve got it sorted.

not a lot of brit bikes where you live
 
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