Author Topic: lean below 3000 RPM *suggestions?  (Read 21765 times)

rainman19154

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lean below 3000 RPM *suggestions?
« on: April 30, 2016, 10:12:59 pm »
'84 VT500 10350 miles
Starts with choke on first crank, holds idle fine.
l have given it mild experimentation but even with choke adjustment, l cannot give it throttle until it's warmed up.

Once warmed up and riding:
Cuts, spits and pops below 3K. Above three thousand, it's OK. Some popping but ridable.
No slow idling along in traffic or mild pull away from a stop. Below 3K it just falls on its face.

Seller told me he was advised that the factory jets are lean and it needs bigger jets. I am disinclined to jump in that direction. It's my opinion that with stock intake and exhaust, the standard jets should be fine.

He said he had the carbs off, so I wonder if he got them well seated when reinstalling.

There may be clogged ports in the carbs- couldn't that create a runnability issue? (No other issues with throttle response or starting)

J6G1Z

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Re: lean below 3000 RPM *suggestions?
« Reply #1 on: April 30, 2016, 11:15:56 pm »
Where are you located? In the USA, or somewhere else?

Typically bikes that were imported into the USA were jetted on the lean side to pass emission requirements. Often one size up on the main jet is beneficial. Fairly normal that it won't respond well until the engine is warmed up.

Is the fuel in your tank fresh, high quality fuel?

It is possible that the carbs internal passages would benefit from soaking in carb cleaner to remove any build up.

The main jets are sized differently. The USA VT500FT has a size #112 main jet in the front cylinders carb & a size #120 in the rear cylinder. I seem to recall one of the forum members using #125 main jets. You might want to search on that.

J.

« Last Edit: April 30, 2016, 11:22:41 pm by J6G1Z »

rainman19154

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Re: lean below 3000 RPM *suggestions?
« Reply #2 on: May 01, 2016, 06:19:24 am »
I am in Philadelphia (19154), so "yes" - I am in the US.

So the lean factory settings is likely an accurate assessment? ... huh.

 And I am also suprised that the front and rear aren't the same- though I have read the rear can run hotter, so perhaps thats a clue as to why the jet size is differant.

rainman19154

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Re: lean below 3000 RPM *suggestions?
« Reply #3 on: May 01, 2016, 07:10:29 am »
Thanks for the immediate input.

I took  your advice and went to Ebay to see what a quick look revealed;

http://www.ebay.com/itm/Honda-VT500FT-VT500-VT-500-V-Twin-Ascot-Custom-Carburetor-Carb-Stage-1-3-Jet-Kit-/252346321886?hash=item3ac1034bde:g:vcoAAOxyYSJSBEVZ&vxp=mtr

would this be overkill? very appropriate? not for the faint of heart?
I am reasonably skilled and have tools (sorry no drill press or machine tools)...

and what about syncing/balancing  the two carbs after rejetting. Is that a concern.
Thanks again.

J6G1Z

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Re: lean below 3000 RPM *suggestions?
« Reply #4 on: May 01, 2016, 09:49:38 am »
I've seen those kits before, but have heard zero feedback on a VT500FT application.

You might want to try calling them on the phone to see what level (if any) of customer service they provide.

I have used a DynaJet kit once. I wasn't overly impressed.

J.