T500 Special Engine (Ported) Rebuild

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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Ok Jim thanks for the suggestion but a bit of a false alarm 8) I feel a bit supid now for not messing with them a bit more but for whatever reason after playing around with them for a little bit they both go down completely to the same level. Not really sure what caused it in the first place though ??? I marked the slides to the carbs and the carbs were brand new a couple of years ago when I built the bike.
I am going to hopefully try running it again today and I will give it a run around the block to get a better idea of what it is doing.
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tz375
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Re: T500 Special Engine (Ported) Rebuild

Post by tz375 »

John,
If they didn't go down fully and it wasn't the throttle stop screws check them carefully to see if there are any small burrs or damage to teh slide or carb bodies.
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

tz375 wrote:John,
If they didn't go down fully and it wasn't the throttle stop screws check them carefully to see if there are any small burrs or damage to teh slide or carb bodies.
I bet you are right that was the issue, going to check the body right now for a burr.
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Couldn't find any thing that looked like it would cause an issue but it seems to be ok now!

Ended up going down to 35 pliots from the 45's as I think the 45's are just so far off, just not sure which direction they are off :shock: I'll fire it up and give it a quick spin when I have the time hopefully it will run better on the low end and the airscrews function as they should :up:
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Ok guys finally had time to switch out the pilots from 45's to 35's. Fired it up again and it seems worse although I was able to get it to tick over. Air screws didn't seem to respond at all still. Just nothing down low. I did ride it around the block this time though and once you get it to clean up it flys :mrgreen: but as soon as you drop the revs back down it has nothing down low :( I think I'll try teazers advice and go the other way and order some 60 pilots. I have to do something! On another note the twin disc set up on the front is bloody awesome, some serious stopping power there :up:
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Re: T500 Special Engine (Ported) Rebuild

Post by dgoodsy »

I hope those jets work for you, or at least get you closer! I can't wait to hear you impressions of the bike when it is well tuned and you can push it a bit!
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

#60 pilots arrived today, hopefully install and test tomorrow :up: Fingers crossed for an improvement!
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Well I finally got the #60 pilots in and fired it up, unfortunately it is way worse with the big jets in there So :wth: far I've tried 35's, 45's and 60's. Going to try throwing the original 25's back in there. Got to do something! I really need a half a day where I can just work on the bike with a box full of jets in front of me. It sounds great when it's on the main jet, I may even have to go a little bigger on those.
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Ok so I fired it up today and she does run better on the 25 pilots. Still not great but I think I will try lowering the needles a little bit to see if that helps. It still seems woolly down low. While it was running I whipped off the uni filters to see if that what make a difference and it seemed to be marginally better. What I noticed is that when you give it a big handful of throttle it seems to initially blast a good amount of vaporized fuel out the back of the carbs.

I will put the filters back on and take it out for a few miles tomorrow to see if it gets any better as I'm riding it. Got to go and pick up some more unleaded race fuel first:)
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Well I rode the 500 today and it was not good. First off it had nothing down low then after about 1/4 mile it started running on one cylinder. Managed to ease it back home and took the carbs off. Left side carb had no gas in it and the left side plug was clean and not burnt at all. Turned the gas tap on and a modest trickle coming from the right side fuel line and only the slightest drible on the left. Disconnected the fuel line at the fuel tap and fuel flow there but not great. Going to remove the tank and check the fuel tap for blockage. I have my single fuel line coming out of the tap to an inline filter then another piece of single line to a Y piece then to the carbs. Not sure why more gas flows to the right side than the left ???
Once I get the gas flowing correctly to the carbs I'm going to reinstall the 35 pilots As I see it there is no reason why the bike shouldn't run half decent with them in there.
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Re: T500 Special Engine (Ported) Rebuild

Post by ConnerVT »

Fuel petcocks aren't rocket surgery. But get that sorted out before making any changes to the carbs.

I looked through some of the pages in the thread, to determine what you have for a petcock. Looks as it isn't a stock, vacuum actuated one, so vacuum isn't the issue. But I went through a few stock petcocks, as well as a cheap Chinese one, before I finally fitted a quality Pingtel. Wish I started with this.

A low fuel level in the bowl will affect how the jetting behaves. While not a critical measurement (both vibration [bumps] and angle [turns] will affect fuel level), the fuel level needs to be correct, else you won't have the correct air/fuel mixture. If the fuel flow to the carb is insufficient, the fuel level will always be low.
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

ConnerVT wrote:Fuel petcocks aren't rocket surgery. But get that sorted out before making any changes to the carbs.

I looked through some of the pages in the thread, to determine what you have for a petcock. Looks as it isn't a stock, vacuum actuated one, so vacuum isn't the issue. But I went through a few stock petcocks, as well as a cheap Chinese one, before I finally fitted a quality Pingtel. Wish I started with this.

A low fuel level in the bowl will affect how the jetting behaves. While not a critical measurement (both vibration [bumps] and angle [turns] will affect fuel level), the fuel level needs to be correct, else you won't have the correct air/fuel mixture. If the fuel flow to the carb is insufficient, the fuel level will always be low.
Thank you. I will be removing the petcock this week to see what is going on. FYI it is a cheap chinese petcock fitted to a custom tank. I may source a quality petcock.
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Re: T500 Special Engine (Ported) Rebuild

Post by Jimroid »

P I N G E L
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johnu
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Re: T500 Special Engine (Ported) Rebuild

Post by johnu »

Well I finally found some time to work on the 500 today! Totally went through the carbs again (got the petcock sorted too) and went back to my starting point for jetting except for using 35 pilots instead of 40's.

Carb settings:
vm34's
Main Jet - 260
Pilot Jet - 35
Needle Jet - Q2
Needle - 6FJ6
Needle clip position - Start in the middle
Slide Cutaway - 2.5

Premix 25:1 ratio using 110 leaded race gas

So I fire it up and starts first kick without using the choke (it's a hot day) so I let it idle for a while to warm up then try rev it a little bit and same old problemnothing down low at all if you coax it to the main jet it is sweet as a nut! So I take the foam uni's off and clean the oiled up plugs and give it another go and it fires right up. Runs slightly better without the filters but not by much :evil: What I notice though is that there just so much atomized fuel coming out the back of the carbs, if you put your hand near the carb just for a second it gets covered!
I'm not really sure what to do next :shock: Not sure if I did something wrong when I built the pipes and they are affecting it somehow but I doubt they could be too far off.
Lot's of head scratching going on :(
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tz375
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Re: T500 Special Engine (Ported) Rebuild

Post by tz375 »

Massive reversion seems to be picking up fuel each time it passes the jets. I don't recall the inlet timing on that motor - it could be too long.

You could also try even smaller pilot jets but that may make the transition to the needle & jet a problem, but one step at a time. How big is the air "jet" that feeds the pilot jet? It should be a fairly large drilling. And air blockage in there would exacerbate the situation
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