Sundial Moto Sports

T500 Special Engine (Ported) Rebuild
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Author:  johnu [ Fri Sep 08, 2017 7:40 pm ]
Post subject:  Re: T500 Special Engine (Ported) Rebuild

tz375 wrote:
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

Dang Richard I wish I lived near you so we could work through it together! I don't understand the air jet drilling, is that where the air screw goes into?

Author:  tz375 [ Sat Sep 09, 2017 5:22 am ]
Post subject:  Re: T500 Special Engine (Ported) Rebuild

I checked through the pics of the build and found your carbs and they look OK in that department. You said it starts OK without choke and idles OK so that actually suggests the pilot jet is a size too large. Main is OK so that suggests one of two things.

Sounds like the needle and needle jet combo is way too rich OR the choke plungers are not seating properly. I found some on a GT750 where the rubber tip of the choke plunger was hard and did not seal properly. It would be worthwhile to check that out. If that's all OK, try a smaller needle jet or thicker needle to see if that makes a difference.

Author:  Zunspec4 [ Sat Sep 09, 2017 12:24 pm ]
Post subject:  Re: T500 Special Engine (Ported) Rebuild

Hi john,

My 2c worth is that the fuel blow back you are experiencing is a normal factor for a piston ported engine. It will be more pronounced if you have advanced the inlet porting with a bit of tuning but will probably almost disappear when the revs rise and the engine resonances begin to work. My race engines do this and you learn to live with it, but it's never too bad. You could always convert to Reed Induction and if you make a few kits I'll be your first customer :up:

Cheers Geoff

Author:  johnu [ Tue Oct 02, 2018 4:21 pm ]
Post subject:  Re: T500 Special Engine (Ported) Rebuild

Hey guys finally got back to working on the 500 and I seem to have it running halfway decent, it is way better than it was before :up: I broke the golden rule and switched two things at once but I think it was a combination of the two anyway. I bought brand new coils and a dual outlet Pingel gas tap. As i say it is running much better now but still rich on the bottom.
Now I have actually been able to ride the bike more than a 1/4 of mile I have realized that the suspension is way too stiff, the handlebars are too far forward, seat is too low and as Teazer pointed out the gearing is too tall. All easy stuff to rectify I think!
Here are a couple of very short video's from last week, I will get better video soon :up:

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