Primary chain tension

How tight can I get away with

Post Reply
Posts: 63
Joined: Tue May 02, 2006 3:40 pm
Bikes: 61FL in a late 49 frame.
59FLH almost stock
Location: Wa state

Primary chain tension


Post by panwars »

Well here we go again. I have fought this new chrome horse trans into the bike, managed to get it aligned with the engine, and bushed so it doesn't slop around in the slots when adjusting. Thought all was cool til I went to put the primary chain on, I have a 24 tooth engine sprocket and with the trans all the way forward hitting the frame (oil tank mount at seat post) and the end of the slots I can just get the chain on. IT IS TIGHT! I can get a 1/2" up and down on the top run but it takes some pressure. It is not a loosy goosy 1/2" This is a new chain that I had run for about 1500 miles before the tear down so it has stretched some already.
Now I have done a whole lot of performance engines (V8s) with dual roller timing chains, and they run tight. Damn tight to start with. What kind of problem will I have running this chain tight? I have already riden the bike and man does this trans work nice. Sure don't want to hurt it though. I could run a 23 tooth engine sprocket and lose some of my upper end speed, but would that loosen it enough? Only other option is complete tear down again, grind top of ratchet housing and lengthen slots in mounting plate, WHAT A BITCH!!!
So once again, how tight can I get away with???? Thanks in advance, Scott

Posts: 796
Joined: Tue Mar 23, 2004 6:57 am
Been thanked: 2 times

Re: Primary chain tension


Post by Billy »

sounds like you already know it's too tight.
The free-play in the chain is necessary as everything gets into Full heat, this free-play lessens, as sprockets expand making things tighter yet. I have seen tranny bearing damage done & of course leaking there as well.
Just my opinion, I would go to the 23T & be safe, & go Bigger if you can on the out-put tranny sprocket. To compensate..
One tooth makes a noticable difference. Then you would have enough free-play......
An New auto Hi-Po dual roller T. Chain can be "Tight"
as it will stretch a bit & the crank & the cam both ride on 'babbit' bushings/called bearings.
No worry about overheating the babbit they are oiled heavily & can take it.

Posts: 452
Joined: Sat Sep 18, 2004 7:21 pm
Location: Roxboro, NC, U.S.A.
Been thanked: 3 times

Re: Primary chain tension


Post by Jack_Hester »

Panwars -

Back in the 70's, when belt drives were in their infancy, I saw the needle rollers in the transmission break up so fine that that they don't even come close to resembling a roller of any kind. Of course, this is the absolute worse condition. One of those where the owner knew something was bad wrong, and drove it the 30 or so miles home. They forced his belt on, with great difficulty. The buddy helping him assured him that it would stretch in just a short while. A really good Gates brand, that used to be known for it's ability to retain it's length for an extremely long time (they were timing belts that were adapted to serve as drive belts). And, I really don't know how long he drove it. Just that he continued to drive rather than haul it. Billy covered the seriousness of the same for chains. And, the fact that you are posting, says that you don't feel right about it. Rather than modify the tranny, do as Billy suggested and drop the engine sprocket to a 23T, and bump the tranny up a tooth. Whole lot of work, but work outside the tranny.


P.S. - That was back in my 'learning' days about non-stock setups. The 70's brought about a lot of experimentation with stuff that didn't exist before. You can't imagine the amount of blame that was put on Harley components, when really it had nothing to do with those components. What little I've seen inside the new stuff shows that Harley has learned to beef up their equipment. It's guaranteed to be modified.

Posts: 50
Joined: Fri Jul 13, 2007 8:03 am
Bikes: 1982 FLHC
Location: NE Illinois

Re: Primary chain tension


Post by 55PAN »

I am also running a 24 tooth motor sprocket and had the same problem. The solution is to contact Chuck at Kick-Start Motorcycle Parts, (616)245-8991 and get a special 84 link primary chain,(the original ones are 82 links) . This should solve your problem.

Post Reply

Return to “Chains & Belts”