SO to make a long story even longer, as a change from the same old twinkie ball and chain, I purchased a 94 heritage with a warmed over evo engine. It came to me sad, and tired, and sorely neglected, but cheap. The sale included a reciept from about 5k previously of an install of pistons, woods 6 cam,mikuni hsr42, and some "Head porting" so not sure of whats really been done. It also had a thunderheader. The bike ran poorly, just sluggish and weak. I replaced the thunderheader with a set of straight shots, no baffles, loud as hell, but thats what I wanted. Been piddling around with the carb and some advance in the timing, and its much better. The engine still seems weak on the top side. Ive changed to a 170 main jet, and it still fades out at wot. Any suggestions?

 

Sad, tired, and neglected usually doesn't equal cheap in the end.

ASSuming all the goodies in the receipt are in the scoot, you should have a decent running little beast there. Cleaning the carb may help more than re-jetting until you know where you are as a start.

I'd start by doing a simple tune up including a compression test, carb cleaning, timing adjustment and see where it is. Some back pressure would help too with open pipes.

Is the ignition stock or aftermarket? Which Woods 6 cam? The W-6 is only a 240 duration and will fall off a bit before redline.

Griz

 

If it doesn't have a healthy VOES, and you advanced the timing to feel good, it might have too much total advance and degrade upper end pull. Depending on the ignition module, curves and how that's set up.

 

Could also be too fat on top. That will make it sluggish.

 

Yup 170 sounds a little big for that.

 

Down here you would run at least 190 with that set up...more likely 200!

My 1998 Wide Glide ran everything stock except an EV27 cam and S&S Muffler....with a Hi-Flo backplate plus a K&N, I not only ran a shimmed needle I ran a 200 main jet and plugs that were a grade colder to stop the plugs looking like bleached bones after a plug chop....ran like a raped ape though...

 

Plenty info here

http://www.mikuni.com/fs-tuning_guide.html

http://www.mikuni.com/pdf/hsr_tuningmanual_021003.pdf

 

Good advice here on the tuning, timing, plugs, carb,,do also agree to add some back pressure to those drags,$20 for drop in power cones. Check voes and vacuum hose.

 

Personally, I'd clean the carb out, put the Thunderheader back on, give the bike some new plugs (iridium), and take it to a shop that has a dyno and someone who knows how to tune a carb and see what she's making hp/tq.

Nothing wrong with 'seat of pants' tuning. I just like to see what the engine is doing through the rpm band and check the A/F ratios.