Primary belt Drives

[afterburn 549]

Shall I or shall I not convert this FLHR Road King to a primary belt drive?
Pros?
Cons?
I need to replace the stater and chain and rear belt as a minimum.
Whilest there should i convert to a primary belt too?
Your thoughts?
Thanx

[kach22i]

This?
2008 Harley-Davidson FLHR Road King

DRIVETRAIN
Primary Drive Chain, 34/46 ratio
Final Drive6 Belt, 32/66 ratio
Clutch 9-plate, wet
Transmission 6-Speed Cruise DriveTM

[afterburn 549]

Originally Posted by kach22i

This?
2008 Harley-Davidson FLHR Road King

Yes, But a older version.

[asphaltgambler]

My answer - no. The stock primary chain and front compensator sprocket do a pretty good job of keeping the drive line smooth-feeling. The problem with primary belt drives is inadequate cooling / lubrication to the clutch pack. Heat, oil contamination and misalignment are the big items to overcome to make the drive belt live, but the bigger problem is clutch plates overheating / warping by not being able to dissipate the heat through an oil bath. They do make 'dry' clutch plates for this but be aware they tend to 'rattle' with the clutch lever pulled in.

On street bikes in the past with stock or moderate HP, you'd run a primary belt set-up mostly to be cool and hear the belt whine (like a supercharger) as it trapped air between the cogs. The wider the belt set-up; the more noise it makes and of course looks very racey.

Drag race bikes use them to reduce rotating / frictional mass, weight and ease of access to service / adjust the clutch spring pressure..

There are guys who will run a small width (1-1/2") primary belt set-up, but keep a somewhat stock appearing primary cover - but spacing it out and having a screen where the clutch derby cover goes to provide airflow.

[afterburn 549]

Thanx asphaltgambler
I was hoping you would insert your opinion.
I was not considering a open belt.
So I guess i did not ask the correct question correct.
If i did convert it, I would ventilate it for sure and run the 1.5 belt. with a cover of sorts
This is a bike with 85 inch axtell cylinders , about 10.5 to 1 CR, with .030 squeesh and DM 530 cam
Machined heads to match pistons.
Runs very nice
I was thinking less weight flopping around in in there would be a good thing and the ride smoother......

[asphaltgambler]

So to be clear - on a heavy street bike (like a dresser) with increased power you'd be installing multiple problems with a primary belt drive, not solving any. The enclosed primary variety are the worse for the above issues.

Of course there are several companies that make them and will sell them to you no problem, but I would leave the stock set-up alone other than replacing the clutch plates and adding a slightly heavier spring from Barnett. To free up some drag and make the clutch action smoother, use Ford ATF (Mercon) instead of the heavy primary oil that is spec'd for it.

Also you should look into slightly lower (higher numerically) final drive gearing. The later bikes have a fairly high (low numerically) final drive that was not present on earlier bikes. The Motor company did this mainly to reduce vibration, noise and increase fuel mileage. I don't remember the actual final drive number, but you should confirm what you have and then look for either: a larger rear pulley or smaller front pulley to achieve @10% reduction (10% higher numerically. This will make a huge difference w/o sacrificing highway speed / RPM

[afterburn 549]

Okie dokie will do
Thanx!

[afterburn 549]

Thats good information.
The RM at 70 is a high.

[afterburn 549]

Many moons ago the (1984?) I bought a wrecked factory 80 inch shovel FLH (the only way i could afford one)
In the refix process I put a primary belt on it, with all the bags and gear except trunk.
I did not own it that long afterwards but rode quite a bit. (All over Eastern Wa )
I do not remeber any pit falls at the time , but it was a long time ago .
I guess with romance in the basket I was thinking it was a good thing....
Thats why I was questioning the procedure for converting now, Cause this thing is going on a 7,000 mile trip this summer.
(and i hate road wrenching )

[asphaltgambler]

An 80" stock shovel engine puts down a whopping 50HP at best and if you don't ride it aggressively - the aftermarket belt set-up was probably as good as what came with it originally in those days. BTW, for about 5 mins, Harley did offer a "duel belt drive" in late '79 - '80 Sturgis FX models. They had big problems right away - mostly alignment / spacer issues between the engine and trans. They ate primary belts like no tomorrow. The factory ended up replacing some with chain conversions to keep their customers happy.

[afterburn 549]

Yes I remeber them,,,,LOL
I will keep the chain, no pain.