Carb Cleaning and rebuilding | GTAMotorcycle.com

Carb Cleaning and rebuilding

Gkaros

Member
Hi all, rebuilding/cleaning carbs off of a Honda VT500FT.
Considering how my previous cleaning totally failed I want to do it right.

I've taken out the

Intake brass things with the filters
2 jets
needles and diaphragms
floats
float needles
bowl drain screws

Questions
A. Don't see ANY o-rings or seals in the carb of ANY sort. I'm sure I saw that the carb gasket kit includes the bowl gasket and 2 o-rings...????? Am I missing something? Are they behind something that isnt obvious?

B. Is the carb cleaner, high pressure compressor method sufficient? or is there a real benefit in paying to put this in some sort of sonic/vibrating machine.

C. This is a stock 500cc non performance bike. Will new jets (jet kit) improve the performance and the way it runs? 6SigmaJets has a kit they claim will improve the bike alot for $50 USD. Not looking for performance but just want it to run like a clock. Is it worth it?


Thanks
 
A. Look on the internets for an exploded diagram, pics of someone else that took it apart or a repair manual. Some gasket kits for sale use stock photos of a generic gasket kit, not necessarily what is actually in that specific kit.
B. I have never had an ultrasonic cleaner when I rebuilt carbs. Clean is clean. If it looks like you got all the gunk out, can get flow through all passages and the jets are super clean you are done. Don't start poking wire through the jets, just lots of cleaner. Hold them up to a light and look through. If you don't see a perfect circle, keep cleaning. People have had good experiences with a cheap chemical cleaner (pine sol, simple green? I don't remember, search GTAM for answer)
C. Assuming that nobody has previously hurt the jets (eg cleaning with a drill bit) and you clean them well, replacing with same size jets won't do anything. Some bikes come from the factory very lean for emissions reasons and adding more fuel makes them run better than new. No idea about your particular bike. Again, the internet is your friend, what have other VT500FT owners done and were they happy with the results. Does 6Sigmajets publish dyno charts or other useful information, or is it just a marketing circle jerk?
 
ok thanks
Im assuming that 6Sigma inflates the benefit to some degree.
If using Jets to make a lean mixture richer (Like what you mention) Is it not that same thing to use the mixture screws to accomplish that.
Why change jets in ANY situation and not change mixture settings?
 
I don't know about that specific carb but on many, the mixture screw adjusts the mixture at mixture at part throttle, the jets set mixture at full throttle. Again, not sure about that carb, but some use a needle in the jet and changing the profile of the needle can change the mixture at varying engine speed/load. It really is amazing how much adjustability is in carbs if you have the time and spare parts to play with them.
 
You most likely want to stay away from re-jetting the bike so no need for the 6Sigma Racing Jet Kit.

Cleaning the carbs:

Disassemble one at a time so that you have the other one as a reference. Take pics. Make notes of air mixture/idle screw settings just in case as a reference.

Soak carb body, bowl, jets, screws, springs, etc. in carb cleaner. Come back occasionally and scrub with an old tooth brush to speed up the removal of old varnished fuel and other crud.
Do not soak non-metal parts like rubber or gasket material.
Be patient. This is not a 5-minute process.
Once they are spotless, spray down all of the jet and air mixture openings with more carb cleaner (from the outside and inside). Make sure to always face the carb away from you so it doesn't go towards your face. You might want to wear eye protection as a precaution.

Before you re-assemble, record the jet and needle sizes for reference. Compare them to those listed in the manual for your bike.

If your jets and needle size are stock, set the air/fuel mixture and idle screws to spec from the manual.

If they are not stock, set the air/fuel mixture and idle screws to the settings that you wrote down before disassembly.

Repeat all steps for carb #2. Don't forget to check jet and needle sizes again. In practice they should be the same but who knows what previous owners may have swapped out.

Finally, do some research on balancing/synchronizing carbs so you can optimize the engine performance. If you need some help there, let us know.


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awesome thanks. For your comment:

Before you re-assemble, record the jet and needle sizes for reference. Compare them to those listed in the manual for your bike.

Are these printed/stamped on the jets?
 
awesome thanks. For your comment:

Before you re-assemble, record the jet and needle sizes for reference. Compare them to those listed in the manual for your bike.

Are these printed/stamped on the jets?

Normally stamped/engraved but not always.

Example
403-203_A.jpg

9_10_08%20028_1.jpg
 
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how to make a diy soda blaster for motorcycle carburetor injector and throttle body cleaning

[video=youtube_share;bBPc5ZFHZP0]http://youtu.be/bBPc5ZFHZP0[/video]
 
how to clean and rebuild a motorcycle carburetor for maximum performance

[video=youtube_share;TGqUAtsP3_o]http://youtu.be/TGqUAtsP3_o[/video]
 
Normally stamped/engraved but not always.

Example
403-203_A.jpg

9_10_08%20028_1.jpg

A few questions; why do you say your previous attempt to clean the carbs was a failure? Is/was the bike running? Does the bike have a modified pipe or airbox?

Carb mixture screws are adjusted to the where the idle speed is highest. Then adjust idle speed to recommended. The mixture screws most effect idle and just off idle. Check your manual for procedure.
The pilot jets effect off idle to almost the midrange. The needle has an effect in the middle rev range and especially steady throttle position - say riding at steady hwy speed. The main jet effects wide open throttle and less down to midrange. All these systems overlap.

When installing carbs make sure both ends of carb are fit perfectly into the rubber intake and exhaust tubes w/o leaks, clamps positioned perfectly all around without any leaks.

more questions; When you removed the float and float needles you make no mention of removing the needle seat. Likely will find a sealing o ring in there.
If your bike is stock check to make sure all the jets are OEM in size. Set the float heights. Did you remove two jets from each carb? (pilot and main). The smaller pilot jet may be sunk in a hole, and regular screwdrivers are too wide to fit in the hole. If this is the case you can take an old screwdriver and use a grinder to narrow the screwdriver shaft so it fits down the hole.

What are the symptons of your bikes problems/driveabilty?

Have a manual for your bike if possible.
 
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OP has another thread suspecting coil issue which moved on to check other reasons why bike wasn't starting which eventually lead to carbs being removed and checked.


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Pine Sol works if you have time to let it soak. Plus side is it won't harm any bits of rubber left on your carb.

If I'm in a rush I use the carb cleaner in a spray can.

Count how many turns to push your adjustment screw all the way in. This will tell you where to set the screw when your putting things back together.
 

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