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Idle troubleshooting checklist? (Back after a long break)

Fuel System: Gas (Petrol) tanks, Carburators
Jlovvorn
honda305.com Member
Posts: 472
Joined: Tue Dec 27, 2011 11:10 am
Location: Washington DC

Idle troubleshooting checklist? (Back after a long break)

Post by Jlovvorn » Mon May 18, 2020 9:19 am

Hey all!

I am back after almost five years!, as I pulled the Superhawk out of storage during the lockdown, and have been bringing her back to life.

Unfortunately, all same gremlins have awoke from hibernation.

I am having the same old, left side doesn't fire at idle, but runs fine above 2k problem.

So at idle it runs fine off the right side between 1000-2000, and the left just pops and fires off and on depending on the air and idle screw setting.

If I bring down the right side under about 1200, it starts to stall.

If you crank the left idle screw in far enough, the left side roars to life and the idle jumps up to 3-4k.

If you then move the right idle down to start balancing, the left eventually cuts out and then the bike stalls.

The left also runs best with the air screw almost closed, which suggests an air leak, but I have not found one.

As long as you keep the right idle high, the bike runs fine. I suspect it would run better if I balanced the carbs, but this is strictly an idle problem.

I fear I have forgotten most of what I know about these bikes! Is anyone willing to offer up a checklist for me?

I know this is a common Honda Twin problem, but what I have looked at online so far hasn't triggered any "ah ha" moments.

So far I have checked the following:

Gas - New - was stored empty and fresh gas added
Spark - New - right brown, left black and fluffy after 30 mins of idle running and troubleshooting
Timing - Electronic, but I guess it could malfunction

Thanks!

PS I found many spare parts during a barn clean-up. If you are in search of a particular 305 or 160 part, hit me up.

DJM
honda305.com Member
Posts: 512
Joined: Thu Oct 09, 2003 1:54 pm
Location: Chesterfield UK

Re: Idle troubleshooting checklist? (Back after a long break)

Post by DJM » Mon May 18, 2020 1:40 pm

Did you check the floats and float heights. Try swapping the two carbs over side to side and see if the problem moves with them.

Jlovvorn
honda305.com Member
Posts: 472
Joined: Tue Dec 27, 2011 11:10 am
Location: Washington DC

Re: Idle troubleshooting checklist? (Back after a long break)

Post by Jlovvorn » Mon May 18, 2020 3:45 pm

Great idea. The Amals did sit for a few years so maybe I should give them an entire going over.

I don't know if left will mount to right, but if so that's a great idea!

Thanks!

DJM
honda305.com Member
Posts: 512
Joined: Thu Oct 09, 2003 1:54 pm
Location: Chesterfield UK

Re: Idle troubleshooting checklist? (Back after a long break)

Post by DJM » Mon May 18, 2020 4:23 pm

Which model Amals do you have, float heights on the comcentrics aren't really adjustable but the float needles are prone to wear, later ones are better as they have Viton ( a type of hard rubber) tips.

Jlovvorn
honda305.com Member
Posts: 472
Joined: Tue Dec 27, 2011 11:10 am
Location: Washington DC

Re: Idle troubleshooting checklist? (Back after a long break)

Post by Jlovvorn » Tue May 19, 2020 8:07 am

They are 626, installed in 2012, but I cannot recall if I got the "premier" version or not.

I can imagine I have clogs from sitting, but not wear. The bike has less than 500 miles on it since the Amals were mounted. I mostly putter around the neighborhood :)

I have had good luck switching my CB160 to replacement PE22. The thing starts on a kick and just goes and goes. Highly recommended to any 160 owners out there - but requires some fabrication of intakes.

There is a PWK 26mm direct replacement for Amal 626, which people use to freshen up Triumph, etc. They are a direct bolt on replacement.

Since the 626 bolted up directly to the CB77, I presume the PWK replacement for 626 might as well.

It's a $200 gamble to try. But I hate to just slap on more carbs without finding the root of my problem.

Of course, if it fixes things like it did on the 160 it would be well-worth it.

If anyone has tried the PWK on a 305 I would love to hear about it. If not, maybe I will give it a try and post the results for others.

Thanks so much for the replies!

DJM
honda305.com Member
Posts: 512
Joined: Thu Oct 09, 2003 1:54 pm
Location: Chesterfield UK

Re: Idle troubleshooting checklist? (Back after a long break)

Post by DJM » Tue May 19, 2020 9:56 am

A contact over here has used a pair of Chinese MOLK or MOLKT carbs on his CB77 with very good results,These are available on line and very reasonably priced. Quality is excellent.
Jetting wise they were spot on 'straight out of the box' , fitting wasn't quit a straight swap but well within the capabilities of anyone with basic skills and equipment.

Only real downside appears to be that the carbs aren't 'handed' which means that adjusters on one side are between the two carbs rather than both being on the 'outside.

PM me for more details, measurements etc.

Jlovvorn
honda305.com Member
Posts: 472
Joined: Tue Dec 27, 2011 11:10 am
Location: Washington DC

Re: Idle troubleshooting checklist? (Back after a long break)

Post by Jlovvorn » Sat May 23, 2020 5:17 pm

Swapped the left and right carbs, except the needles, slides, and tops.
The problem did NOT move from left side to right with the carb.
The problem is still present on the left but significantly better.
Right side runs exactly as before - perfect down the line.
Will hold idle at 2k, but left side pops and backfires at idle and during deceleration regardless of air screw setting. Closed seems to help.
Will not hold idle under 2k without occasional left side dropouts and stalls.
Left Plug is normal but perhaps a bit wet.
Idle also is slow to come down on left side and hangs around 3-4K and then drop quickly, which makes me fear an advance spring issue.
I thought I fixed that damn thing years ago.
Acceleration and power are fine up to 35mph. (Ie, about as fast as I can go on my farm driveway)
So, it runs but not well.

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