I can´t setting up my carbs to 10 in Hg at 1200 rpm..why???

[Eliseo Monteverde]

I am trying to synch the carbs to 25 cm Hg (10 in Hg), follwing step by step Earl and BWringer instructions,but I can only draw 18 cm Hg (7.2 in Hg) at 1200 RPM.

Also when I ride the bike from 0 to 1/3 throtle the bike has an erratic aceleration...that is why I am working on carbs.

Before top en rebuild I havent that problem.

Mixture was setting up by the highest method hearing the exhaust noise, looking the rpms instrument and the mercury level.

It is a 650 katana with bs 32 ss CV carbs (cleaned and float level at 23 mm.).
Top end has been recently rebuilded.
Stock jets and air filter.
Air filter is clean.
No air leaks.
New plugs, half electrode is dark and the other half is slighty brown.
Valves has the correct clearence.

I am doing something wrong? :?
Or it has several little problems? 8O

Thanks and happy Christmas.

Eliseo.

 

[Philly_Chris]

I thought you are supposed to sync the carbs using a higher RPM 2000 or 2500 to smooth things out

 

[earlfor]

The carbs can be synched at any rpm you wish. The problem is that the higher the rpm, the quicker the heat build up and if you work slowly, the engine will become overheated. Besides the possibility of engine damage, an overheated engine will not synch accurately. I think its a better idea to snych at, or around idle rpm until a bit of experience is acquired. My proceedure is to synch at 1200 rpm to get everything smoothed out. Then, the next day, I go back and re synch the bike for the rpm I operate it at primarily. That means doing a synch at 4500 rpm or so. No fan is going to keep it cool at that rpm. Basically, you have 60 seconds max before heat build up will effect the synch. My best time for synching four carbs is about 15 seconds.



Earl

I thought you are supposed to sync the carbs using a higher RPM 2000 or 2500 to smooth things out

 

[earlfor]

Re: I can?t setting up my carbs to 10 in Hg at 1200 rpm..why

Re: I can?t setting up my carbs to 10 in Hg at 1200 rpm..why

To get accurate plug reads, the first thing needed is getting the vacuum levels on all carbs the same. My bikes draw around 25 cm hg @ 1200 rpm, but yours my be slightly different. It isnt cast in stone. Get them all the same and take the bike for a test ride and then look at the plugs. By "all the same" I mean all vacuum levels within a 1/2 cm range.

Earl

I am trying to synch the carbs to 25 cm Hg (10 in Hg), follwing step by step Earl and BWringer instructions,but I can only draw 18 cm Hg (7.2 in Hg) at 1200 RPM.

 

[Eliseo Monteverde]

My best time for synching four carbs is about 15 seconds.

WOW!!!! 8O there is no doubt that you are very experienced working on carbs......You should be in the records guinnes :!: :!: :!:

Ok, Thanks Philly and Earl for help me.
I am in my first experience balancing carbs, so it takes me several minutes....of course I have a fan near the engine for cooling.

To get accurate plug reads, the first thing needed is getting the vacuum levels on all carbs the same. My bikes draw around 25 cm hg @ 1200 rpm, but yours my be slightly different. It isnt cast in stone. Get them all the same and take the bike for a test ride and then look at the plugs. By "all the same" I mean all vacuum levels within a 1/2 cm range.

I have the four carbs exactly at 18 cm Hg idling at 1200 rpm with a 1/2cm (or less) of difference.
The bike runs much better, some vibration has disappeared and the engine seems to be more powerful.
But the problem from 0 to 1/3 or 1/4 throtle in 1 and 2 gears has not disappeared. :?
Plugs has the same reading than before.

Any idea?

 

[earlfor]

"But the problem from 0 to 1/3 or 1/4 throtle in 1 and 2 gears has not disappeared. " ............... At low rpm, the bike consumes more electricity than it makes. If your battery voltage is low, rough running, and missing could occur in the lower rpms. Once the engine rpm is high, the stator produces enough power to run everything. I would check battery voltage at the battery terminals and at the positive leads to the coils. Battery voltage should be at least 12.5 volts. Voltage at the coil leads (usually orange/white wire) should not be less than 12.

Earl

I have the four carbs exactly at 18 cm Hg idling at 1200 rpm with a 1/2cm (or less) of difference.
The bike runs much better, some vibration has disappeared and the engine seems to be more powerful.
But the problem from 0 to 1/3 or 1/4 throtle in 1 and 2 gears has not disappeared. :?
Plugs has the same reading than before.

Any idea?

 

[Eliseo Monteverde]

Ok.....

Battery voltage was cheked and it is ok, coils too, so electrics is not the problem. :lol:

I re synched carbs at 3000 rpm, now I have 22 cm Hg, but when I let them idle at 1100 the four mercury columns aren?t at the same level than at 3000 rpm...that it is normal?...but the bike has not any vibration at any rpm...that is good.

Also I change the mixture screw setting,they are at 1.5 turns out and change the needle?s circlip to the middle position because they was at the 5th grove.

Spark plug 1 and 4 are tan coloured.

Spark plug 2 totally fouled black coloured :twisted:

Spark plug 3 brown coloured :?

The porblem from 0 to 1/8 throttle continues, but it seems to disapear when I ride with the petcok on PRI position.

Do you think that is a petcock problem because carb n? 2 is burning to much gas? :?

 

[earlfor]

"I re synched carbs at 3000 rpm, now I have 22 cm Hg, but when I let them idle at 1100 the four mercury columns aren?t at the same level than at 3000 rpm...that it is normal?...but the bike has not any vibration at any rpm...that is good." ----------------- Its normal for the synch to change slightly at different rpms and come into exact tune at the rpm you did the synch at. -----------


"Spark plug 1 and 4 are tan coloured.

Spark plug 2 totally fouled black coloured :twisted:

Spark plug 3 brown coloured :?"----------------------------- I would check resistance between the spark plug caps on the 2,3 coil. It should be between 15k and 40K ohms. If youre using Dyna coils with 5k resistor caps, resistance will be about 15K. If youre using old stock coils and resistor caps, it will be around 30K. Anything up to about 40K ohms resistance is acceptable. You can also unscrew your plug caps and check them individually. Each cap should have 5k resistance. I would also check the float height setting on the 2 and 3 float bowls. Too high a fuel level will also cause rich runing and fouling plugs.

Check the ignition timing on the 2,3 side. If the timing is retarted, that too can result in incomplete combustion and black plugs.

Earl

Ok.....

Battery voltage was cheked and it is ok, coils too, so electrics is not the problem. :lol:

I re synched carbs at 3000 rpm, now I have 22 cm Hg, but when I let them idle at 1100 the four mercury columns aren?t at the same level than at 3000 rpm...that it is normal?...but the bike has not any vibration at any rpm...that is good.

Also I change the mixture screw setting,they are at 1.5 turns out and change the needle?s circlip to the middle position because they was at the 5th grove.

Spark plug 1 and 4 are tan coloured.

Spark plug 2 totally fouled black coloured :twisted:

Spark plug 3 brown coloured :?

The porblem from 0 to 1/8 throttle continues, but it seems to disapear when I ride with the petcok on PRI position.

Do you think that is a petcock problem because carb n? 2 is burning to much gas? :?

 

[Eliseo Monteverde]

Dear Earlfor,

I have checked resistences yesterday ,and seems that everything is ok.

The fuel level is at 5 mm below from the gasket surface in all the carburators.I have measured it from the external with a plastic hose screwed at the drain hole.

Also cheked the petcock?s diaphragm and it only needs to replace the little "o"ring.

Once a time I have finished those inspections I went for a ride...
But still the "hesitation" at low throtle was there....so I decided to ride a little hard......
After that I inspected the plugs and voila!!!the four were tan colored!!!! ..exactilly I dont know why.

Today before crank the engine I inspected the plugs again and found crude fuel on plug n? 2

Went for a ride again and the hesitation is story.

Now I am wondering why and how that fuel was in the combustion chamber?
I would not like a crankase full of fresh oil and gas.

What do you think?

 

[earlfor]

OK then, you said...."
Once a time I have finished those inspections I went for a ride...
But still the "hesitation" at low throtle was there....so I decided to ride a little hard......
After that I inspected the plugs and voila!!!the four were tan colored!!!! ..exactilly I dont know why.

Today before crank the engine I inspected the plugs again and found crude fuel on plug n? 2"
.............................................. On the 750 I used to have, the petcock vacuum line was attached to the number 2 carb. If there was a petcock diaphram/"O" ring leak, fuel would enter the engine into the 2 cylinder through the vacuum line. Some bikes have the petcock vacuum line attachedc to the 3 cylinder. If yours does, then the petcok is not the problem causing the 2 cylinder to be wet. If your vacuum line is connected to the 2 cylinder like mine was, then I suspect your #2 plug problem is because of a faulty petcock. that may also explain why the plugs all will burn a tan color if you run the bike hard, but foul the number two with easy running. High throttle settings can burn off the excess fuel getting to number two. At low throttle settings, the leak is a greater percentage of the total fuel needed by the cylinder. I would try capping off the vacuum line and riding the bike with the petcock on prime to see if this cures the number 2 fouling problem. Be sure to switch the petcock back to the run position when turning off the engine because prime is gravity feed and fuel will flow regardless of if the engine is running or not.
On the run position, fuel should not flow with the engine not running.

Earl

Dear Earlfor,

I have checked resistences yesterday ,and seems that everything is ok.

The fuel level is at 5 mm below from the gasket surface in all the carburators.I have measured it from the external with a plastic hose screwed at the drain hole.

Also cheked the petcock?s diaphragm and it only needs to replace the little "o"ring.

Once a time I have finished those inspections I went for a ride...
But still the "hesitation" at low throtle was there....so I decided to ride a little hard......
After that I inspected the plugs and voila!!!the four were tan colored!!!! ..exactilly I dont know why.

Today before crank the engine I inspected the plugs again and found crude fuel on plug n? 2

Went for a ride again and the hesitation is story.

Now I am wondering why and how that fuel was in the combustion chamber?
I would not like a crankase full of fresh oil and gas.

What do you think?

 

[Eliseo Monteverde]

Thanks a lot Earl :!: :!: :!: :!:

Yes I have the petcock vacuum line attached to the #2 cylinder.

I wish you a happy New Year!!!!!!

 

[earlfor]

Happy New Year to you too.

Earl

Thanks a lot Earl :!: :!: :!: :!:

Yes I have the petcock vacuum line attached to the #2 cylinder.

I wish you a happy New Year!!!!!!