Hi guys:
If you remember, I wanted my 2000 Roadstar to be capable of shifting at the shift points recommended in the manual.
I recently installed a Dyna D3K7-3 and set it to the highest advance curve, and full retard(the last 3 dip switches "ON". My Roadstar can now be shifted into 5th gear at 30mph, and will pull smoothly when the throttle is rolled on. Mind you, at those low revs you can feel every power stroke, but that is not unpleasant. Before anyone gets excited, I don't normally shift at those low shift points, but it is nice to have a broad speed range in 5th gear, and not have to constantly be shifting gears.
My Roadstar is now the relaxed cruiser that I expected when I bought it, and it is still capable of accelerating quicker, and going faster, than I will ever require

Wow, My Roadie absolutely HATES BEING LUGGED. She'll protest if I even try to use 5th gear at speeds lower than 80km/h (50mph) ....I don't rev the crap out of it beforr upshifting either....
Those goofy recommended upshift points in the Yamaha owners manual are way outa whack!
When you get an engine bucking at low RPM's it means it's running too slow under load to be happy.
One reason for the bucking is that the air and fuel don't mix properly and therefore don't burn properly. The other reason for bucking is spark timing, cam/valve timing and "flame-speed" of combustion. Severe lugging is very hard on con-rod bearings, rings. pistons, etc.
An air cooled motor can't cool or lubricate itself effectively while in ligging conditions under load.
Lugging also can lead to excessive carbon deposits due to improper combustion and expulsion of combustion byproducts.

Any engine engine will only perform within a limited RPM range according to the way all is set up.
This is why those high-RPM racing engines in cars will not idle properly at 700 RPM (they buck, and surge at idle because the cam-grind and spark timing at all set to run at 3,000 to 6,000 RPM's ideally.

Just my two-cents worth on the subject. Hay Bay Woody has a good point on broadening the useable torque-band of the engine.
I recurved the injection timing advance on my '93 Cummins diesel so it will now pull like crazy from 1400 to 2900 RPM and still sound happy doing it at 711 ft/lbs peak torque.
Stock setup was a VERY NARROW TORQUE BAND with 400 ft/lbs torque only betweem 1700 to 1900 RPM. They did this to meet emission requirements. At 2,000 RPM it was out of steam and not sounding happy (117km/h) This narrow stock torque-band was frustrating with only a 5 spped tranny with large split beteween gear ratios on upshifting, 3rd was screaming and 4th was lugging when pulling 16,000 lbs. upshifting on steeper hills. I probably make a little more greenhouse gas now, but it is a way more driveable towing rig now!
It's all in the details of how you set it up.
...Now it pulls like a champ all the way till the governor cuts in at 2950 RPM. (172 km/h)

The last two dip switches are for the retard. If you have a stock setup the retard swithes are non functional.

I agree with Myram ... you asking for trouble running the engine under load at low rpm.

Doc

DocShadow wrote:
The last two dip switches are for the retard. If you have a stock setup the retard swithes are non functional.

I agree with Myram ... you asking for trouble running the engine under load at low rpm.

Doc
Hello Doc:
The reason the retard switches are functional in my case, is because I have disconnected the TPS, defaulting the timing to WOT.
The danger of working an engine at too low an RPM is the possibiliy of low oil pressure, however, Yamaha purposely designed an under-square, low RPM, pushrod, tractor type engine for the Roadstar. Engines which are designed to produce their horsepower with high revs, must have a short stroke in order to keep the piston speed low. Piston speed-per-RPM increases with stroke length, and wear increases with piston speed. It is a myth that lugging is harder on an engine than revving.
What do you think?