1962 650ss Build

texasSlick said:

So ..... do I understand what I see in these pics?

Two fuel taps are feeding one float chamber (left side) via a dual banjo. Nothing to be gained by that arrangement. The needle and seat are the limiter to fuel flow. One fuel drop will be adequate.
I assume the right carb is a chopped Amal and is fed by a tube between banjos on the jet blocks.

The center stand spring can be managed by pressing washers between the coils to extend the spring. Once the spring is on the stud, the washers can be pushed out.

Slick

Click to expand...

The washers in the centre stand spring has always worked well for me
Bend the spring one way pop the washers in
Then bend the other way and do the same
Then pull them out one by one with pliers when the spring is on

seanalex said:

Yes you are correct the right carb is chopped. So there should be enough fuel to flow just from one line to keep the float bowl up? Makes me think that maybe the hose that I had between the two jet holders was Kinked that bad.

The other thing thats creeping into my mind is if the Auto Advance is not opening and closing properly, thus throwing off the timing at a higher RPM.

Just to rule out Timing as the issue, if the engine starts easily, and Idles quite smoothly, is that enough evidence that timing is where it should be? Its also just occurred to me, that now would be the ideal time to recheck the Timing since I have the entire primary off already.

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The AAU has a tendency to stick open at low rpm, particularly if the timing chain tension is too tight. This condition does not affect high rpm.
If the engine starts easily and idles smoothly, the timing is likely right or close enough. A timing check with the primary off is easy to do. A detailed how to is here - be particularly careful to ensure the timing is correct on both ramps:


Regarding fuel flow, here is info that shows the needle and seat are the bottlenecks in the fuel delivery system. In a previous thread, it was estimated that a hot Norton twin engine will gobble up about a pint per minute (473 ml/min) at full load. Thus the engine will starve for fuel at high rpm/high load conditions if the needle and seat cannot pass that much. An examination of my data shows the typical Monoblock needle and seat with a 0.125 inch orifice is insufficient.


Slick

texasSlick said:

The AAU has a tendency to stick open at low rpm, particularly if the timing chain tension is too tight. This condition does not affect high rpm.
If the engine starts easily and idles smoothly, the timing is likely right or close enough. A timing check with the primary off is easy to do. A detailed how to is here - be particularly careful to ensure the timing is correct on both ramps:

Setting up and Timing a K2F Magneto

It seems like this topic keeps coming up, and I have to write it over and over. Hopefully, one comprehensive discourse will settle it. If anyone finds anything confusing, please let me know so I can revise. The following procedure assumes the magneto armature is properly centered and aligned...

www.accessnorton.com

Regarding fuel flow, here is info that shows the needle and seat are the bottlenecks in the fuel delivery system. In a previous thread, it was estimated that a hot Norton twin engine will gobble up about a pint per minute (473 ml/min) at full load. Thus the engine will starve for fuel at high rpm/high load conditions if the needle and seat cannot pass that much. An examination of my data shows the typical Monoblock needle and seat with a 0.125 inch orifice is insufficient.

Flow Measurements on Ewarts Fuel Tap

A thread on the Commando Forum piqued my interest to make some flow measurements on an Ewarts fuel tap as used on the Atlas. The tap is pull for Main, and twist 90 deg. for Reserve. I measured the fuel delivery to the float chamber of the Monobloc carburetor, which included flow resistance...

www.accessnorton.com

Slick

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This is great, thanks for the link to the article about fuel flow @slick, and I'm a bit relieved with your comment about the timing and the AAU.

If I'm following that thread you linked to correctly, and as you're saying above the 0.125 needle would be way too small for what I'm trying to do. I have a decent set of petcocks on the bike, I should check the flow rate I suppose, but I really think this Needle size could be my issue.

Looking at the old set of needles that I have (the ones currently in the bike are 0.125 I'm almost positive as I bought them during the rebuild) at what point do I measure? At the needles straightest part mine reads a hair under 0.1". Looking through a bit more posts that seems to be the "standard size". I see that Burlens sells "C2" needles, and they have that listed for alcohol.

any ideas or leads on where to find the next larger size needles? Burlens sells them, but the shipping is absolutely insane. 33gbp for 2 needles to ship.

If I do increase, should I also be looking to bump my needle jets up to 107?

seanalex said:

This is great, thanks for the link to the article about fuel flow @slick, and I'm a bit relieved with your comment about the timing and the AAU.

If I'm following that thread you linked to correctly, and as you're saying above the 0.125 needle would be way too small for what I'm trying to do. I have a decent set of petcocks on the bike, I should check the flow rate I suppose, but I really think this Needle size could be my issue.

Looking at the old set of needles that I have (the ones currently in the bike are 0.125 I'm almost positive as I bought them during the rebuild) at what point do I measure? At the needles straightest part mine reads a hair under 0.1". Looking through a bit more posts that seems to be the "standard size". I see that Burlens sells "C2" needles, and they have that listed for alcohol.

any ideas or leads on where to find the next larger size needles? Burlens sells them, but the shipping is absolutely insane. 33gbp for 2 needles to ship.

If I do increase, should I also be looking to bump my needle jets up to 107?

Click to expand...

You measure the orifice size in the seat by passing a drill thru it.

You can get an alcohol needle from Burlen which should work in a 0.156 " bore seat. I spoke with a Burlen tech support guy about why they did not offer a corresponding seat for the alcohol needle. His response was "Just drill out the 0.125" seat to 0.156". If I were to do that, I would drill from the top side down, then carefully deburr the seat with a larger drill. Extrapolating my data, yields an estimated flow with a 0.156" orifice seat of over 400 ml/min.

There is no need to alter any of the carb jetting when replacing a needle and seat with one having a larger orifice.

Slick

texasSlick said:

You measure the orifice size in the seat by passing a drill thru it.

You can get an alcohol needle from Burlen which should work in a 0.156 " bore seat. I spoke with a Burlen tech support guy about why they did not offer a corresponding seat for the alcohol needle. His response was "Just drill out the 0.125" seat to 0.156". If I were to do that, I would drill from the top side down, then carefully deburr the seat with a larger drill. Extrapolating my data, yields an estimated flow with a 0.156" orifice seat of over 400 ml/min.

There is no need to alter any of the carb jetting when replacing a needle and seat with one having a larger orifice.

Slick

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Ok. I now see what you’re saying. I was thinking “needle”

Now I’m understanding and Taking off the needle seat. Enlarging now.

So. It’s now been enlarged.

Here’s a new problem and I’m curious if anyone has an idea for a remedy.

The float needle tip now doesn’t seal the hole. It looks like it’s letting a small bit of fuel past. Then it begins to flood from the tickler.

Curious how I can solve this. Any thoughts?

seanalex said:

So. It’s now been enlarged.

Here’s a new problem and I’m curious if anyone has an idea for a remedy.

The float needle tip now doesn’t seal the hole. It looks like it’s letting a small bit of fuel past. Then it begins to flood from the tickler.

Curious how I can solve this. Any thoughts?

Click to expand...

Is the new seat the same taper?

I'm guessing its not.

I just went straight through with the larger drill. Stepping up in bit sizes one at a time. In re-reading the above post from slick, I hope its possible to cut just a little bit with the next size up bit? I'm wondering if there is enough of the Viton tip to seal up whatever taper I can achieve.

But, if its not already sealing this current hole, there's no way it will seal something larger.

Well, I never said I agreed with the Burlen tech that it was a cinch to drill out a seat, but he implied that it was.

Hopefully, you only have a burr on the edge holding the needle off. Try twisting a larger drill bit around the orifice with your fingers.

You are using the alcohol needle? The 0.125" needle in a larger orifice is not likely to seal.

The proper remedy is to lap the seat with a tool having the proper taper. Dunno where you will get one of those. Good luck with it.

Slick

Haha, yeah, all good. Already had the replacement on order before I attempted to drill it. Also have the alcohol seat, and needle coming from Baxters.

Going back on it, I did just that with the larger drill bit and a tiny bit of cutting oil. Did it just by hand, and its made a nice little purchase. Hopefully the pieces from Baxters all fit together.

Alcohol seats and needles are designed for alcohol. They’re bigger cos they have to flow MUCH more fuel.

I can’t see why you feel the need to do this? You have a fairly standard 650 motor and there must be thousands of them running nicely with stock monoblocks.

Why do you think this is a problem that needs solving ?

You make a valid point. Was just after why it seems to be running out of fuel or not getting enough flow.

I just need to take two steps back from this, and approach it one thing at a time. Have to come to the realization I will not be riding this bike in a day or so. Just getting eager.

seanalex said:

You make a valid point. Was just after why it seems to be running out of fuel or not getting enough flow.

I just need to take two steps back from this, and approach it one thing at a time. Have to come to the realization I will not be riding this bike in a day or so. Just getting eager.

Click to expand...

Well, too big a hole isn't itself a problem, unless it doesn't seal. I'm with @texasSlick thinking a burr or the like on the seat is the problem. Perhaps wrap a bit in tape so as to not scrape the sides of the bore, just only scrape the seat to remove a burr.

Fast Eddie said:

Alcohol seats and needles are designed for alcohol. They’re bigger cos they have to flow MUCH more fuel.

I can’t see why you feel the need to do this? You have a fairly standard 650 motor and there must be thousands of them running nicely with stock monoblocks.

Why do you think this is a problem that needs solving ?

Click to expand...

FE, IIRC, you were the one who, in a previous thread estimated a hot Norton twin, required about a pint of fuel per minute.. It was that thread that induced me to perform flow measurements on my fuel tap and needle seats. Those measurements show the typical 0.125" seat is insufficient.

In my experience, the Atlas was long criticized for losing its push over 4500 rpm, a condition mine never suffered from. But then, my Atlas, bought new from a dealer, was inexplicitly fitted with a needle and seat having an orifice of 0.200".

You also know many Monobloc owners knew something was amiss in the fuel delivery system, and attempted to remedy the issue by installing extended fuel chamber covers, which you have stated merely delays the problem, not solves it.

Thus, you know what seanalex is trying to accomplish! He thinks he is running out of gas at high load, high rpm conditions, as I think he is, and as were all the Atlas's I ran away from in my youth.

@seanalex: The Burlen guy I talked with said the alcohol seat was no longer in production. I am curious as to the part number on the part you have on order from Baxters. The needle part number would be good to know as well.

The 0.200" needle and seat on my Atlas, is as far as I can determine, an aftermarket part made by a now defunct company called Webbco, or Webco. How it got on my Atlas is a mystery, as is several other anamolies on my bike.

Slick

It wasn’t me that came up with the pint a minute calculation, but yes, I have been one who has suffered fuel flow issues that cause fuel starvation.

But… it is a sustained WOT condition, and I thought Sean was still bedding in his new build?

I do take care to ensure good flow taps etc on my Norton, but it’s a 920 being fed by 35mm FCRs. The fuel starvation issues mentioned above were on a 1000 Vincent fitted with 30mm Mikunis... and if you speak to a Mikuni expert you’ll know that those carbs were never designed to feed 500cc each!

So yes, I’m with you on the whole ‘take care to avoid fuel starvation‘ topic, but was not / am not sure it is Sean’s problem.

Links to the part numbers via Baxter.

expanded Amal part numbers monobloc

alcohol float needle p# 376/161
alcohol seat p# 376/118

We'll see how it goes when the pieces show up. I'm going to try it both ways. With the stock .125 and whatever the enlarged one is.

Actually, I am not SURE it is his problem, but I think it is a good issue to put to rest.

Slick

@seanalex

Thanks for the needle and seat info. I note that the alcohol seat description only states "0-125" . That smacks of the orifice being 0.125" id. I hope I am wrong about that. Let us know when the parts arrive.

I also note the pic of the needle resembles more a standard needle. I have an alcohol needle and remember it being different from a standard.i am not now with my parts bin so I cannot verify.

Slick

texasSlick said:

@seanalex

Thanks for the needle and seat info. I note that the alcohol seat description only states "0-125" . That smacks of the orifice being 0.125" id. I hope I am wrong about that. Let us know when the parts arrive.

I also note the pic of the needle resembles more a standard needle. I have an alcohol needle and remember it being different from a standard.i am not now with my parts bin so I cannot verify.

Slick

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It will probably get here Tuesday. I thought the same thing about the 0-125 and about the alcohol needle photo. But they carry two different part numbers for each of those pieces.

Will measure and post photo of whatever shows up.

Parts came from Baxter. Kind of hard to get a detailed photo of something so small.

Float needles From left: Alcohol, Standard, Viton Tip



Left side stock. Right side alcohol seat.


Left side stock. Right side alcohol seat. Left side measures 0.1" Right side measures 0.14"