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3crispies
Samba Member
Joined: March 08, 2019
Posts: 128
Location: Cambs UK
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 Posted: Sun Jan 10, 2021 1:14 pm Post subject: CB singleport issues maybe |
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Fitted these for our Icts in the summer had loads of issues sealing them properly. Ruined supplied crush washers and fitted others all was well but seem to have running/starting issues. Cold starting just wont rev or tickover for ages but once warm runs but no very smooth. Had a quick spray with leak spray and didnt see obvious leak but not sure if Im chasing the wrong issue.
Everything else seems good- new motor-fully cleaned and set up carbs- spark nice and blue-no obvious exhaust or backfires-valves set-malpassi regulator @ 2.1psi
Plan on upping 55 idle to 57 and checking plugs as cant remember make etc.
Option is fitting new original crush washers and some sort of elring sealer but never uses this on new heads/manfolds before... |
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67rustavenger
Samba Member
Joined: February 24, 2015
Posts: 11036
Location: Oregon
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| Posted: Sun Jan 10, 2021 1:59 pm Post subject: Re: CB singleport issues maybe |
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Do you have a balance tube between the intake manifolds? It helps with smoothing the idle.
Dual carbs run a little rough when the engine is just started. Then once the manifolds warm up a bit. The engine runs much better/smoother.
What's your ignition timing set at, at 3300RPM? Ideally, you should be between 28° to 30° advance.
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3crispies
Samba Member
Joined: March 08, 2019
Posts: 128
Location: Cambs UK
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| Posted: Sun Jan 10, 2021 3:02 pm Post subject: Re: CB singleport issues maybe |
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| 67rustavenger wrote: |
Do you have a balance tube between the intake manifolds? It helps with smoothing the idle.
Dual carbs run a little rough when the engine is just started. Then once the manifolds warm up a bit. The engine runs much better/smoother.
What's your ignition timing set at, at 3300RPM? Ideally, you should be between 28° to 30° advance. |
yeah balance pipe, set at 28 deg advance even checked vac advance can is working and have a good squirt of fuel in both carbs. The engine wont rev or tickover until fully warmed up just tries to cut out, fires by pumping accelerator loads. I tweaked mixture a little but am I right if has an air leak will weaken mixture ? |
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modok
Samba Member
Joined: October 30, 2009
Posts: 27658
Location: Colorado Springs
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| Posted: Sun Jan 10, 2021 5:40 pm Post subject: Re: CB singleport issues maybe |
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1500 SP manifolds had a separate flange with some Teeter-totter action, which gives even pressure.
I made a bigger steel SP manifold and welded it solid for bigger diameter, so...... I guess the nuts have to be tightened evenly at the same time, and so that's what I did, which is possible thanks to having two hands.
Next time I think I will make a teeter-totter type hold down flange, or just machine the head flat and use a normal flange which does not have a tilting problem. |
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