Topic: brandEn's K4

[brandEn]

Wheel looks nice, digging that trolley stand for TAO.

Which Avons are you using on TAO, how do you like them and how are they wearing?  What sizes and pressures are you running?

Thanks for the polishing props, it is therapy for now.

David

TAO is running Avon RoadRiders. I am very happy with them. They only have about 3000 miles but so far so good. Rear is 120/90-18 and front is 90/90-19. I think the pressures are around 35 to 40 rear and 32-35 front measured cold.

[brandEn]

That rear stand is from Discount Ramps. They always have ads in every motorcycle mag. I got it for about $100 shipped. Its pretty handy so far and seems sturdy enough.


Black Widow Rear Spool Trolley Stand

[SOHC4 Cafe Racer Fan]

Thanks Branden. I have a Pitbull for my RC51 but I like the trolley feature on yours. I am also using a Carpy swing arm after my last builder pilfered my genuine Dresda swing arm.

[sazaver]

One more piece to the puzzle got installed today.


The 754 chain oiler plug.
THANKS FRANK! I took some pictures for you.
 


I thought about installing it with some Hi-Temp RTV on the threads but it was such a tight and perfect fit I don't think its really necessary. I just lubed the o-ring with engine oil.

What is the function of this plug? is it a replacement  for an OEM part or just to make "things" easier?

[brandEn]

Installed new sleeve bearings in my carb backplates today. Fit was perfect and the material is way better than OEM. This should be a permanent fix. Thanks Lucky. You do need to order 4 of them though and the cost shipped is about $18.

[brandEn]

I should also have a few more project updates coming soon. Speedo and tach rebuild and front fork rebuild. Looking forward to these.

Quick Question:
CB750 + Progressive Fork Springs = how much fluid?
Can't get a solid answer on this but I would like to know what has worked for others. The progressive springs will take up more space so I think less fluid should be used. ANY INPUT WOULD BE GREAT!!!! Help a brotha out!

[MCRider]

I should also have a few more project updates coming soon. Speedo and tach rebuild and front fork rebuild. Looking forward to these.

Quick Question:
CB750 + Progressive Fork Springs = how much fluid?
Can't get a solid answer on this but I would like to know what has worked for others. The progressive springs will take up more space so I think less fluid should be used. ANY INPUT WOULD BE GREAT!!!! Help a brotha out!

Curious why you think the springs will take more space? Anyway put the tight winds on top. LEss interference with oil level and less unsprung weight.  Other than that, use the lower end of the range in the manual and add as needed.

[Jerry Rxman Griffin aka MuthaF'er]

I went with the same amount. Don't see any reason to do otherwise. Less may be unsafe IMO.

[brandEn]

I figured the tighter end went down, thus displacing more fluid.

[MCRider]

I figured the tighter end went down, thus displacing more fluid.

Its a bone of contention, IKON puts them down. But i was taught and Progressive recommends, for the reasons I mentioned, tight end goes up.

http://forums.sohc4.net/index.php?topic=12054.0

PS: I see at the end of the thread that Progressive recommends down, reverse of what I had.  Bottom line doesn't matter. I prefer up.

[Flying J]

Not to highjack but putting the tighterwound end down would give you less un sprung weight because its the first part to compress so it would be the only part moving as sprung weight on smaller bumps. In comparison,  If you put the tighter wound end at the top it still is the first to compress but now when it does the more stiff length of the spring below is moving up and down with it as sprung weight. Thats how it works in my head. Could be wrong though just thought it was interesting.

[andy750]

I went with the same amount. Don't see any reason to do otherwise. Less may be unsafe IMO.

Same here and used a 1` PVC spacer on top though it was a tight squeeze.

[MCRider]

Not to highjack but putting the tighterwound end down would give you less un sprung weight because its the first part to compress so it would be the only part moving as sprung weight on smaller bumps. In comparison,  If you put the tighter wound end at the top it still is the first to compress but now when it does the more stiff length of the spring below is moving up and down with it as sprung weight. Thats how it works in my head. Could be wrong though just thought it was interesting.

I don't think so. Unsprung weight is that weight which is below the point of measurement. It is the weight of the things that move. Like the wheel, the lower legs, and the lower half of the spring. In the case of a progressively wound spring, the heaviest half is the half with the tighter coils. So it should go up.

That's how I learnt it anyways.  A google search seems to suppport me, but raises questions as well.

Hmmm PS: I'm seeing your point. No time to confirm now though.

[MCRider]

http://www.progressivesuspension.com/pdfs/forkSprings/3055.pdf

Says it doesn't matter to performacne of spring, but does not address unsprung weight.

[Flying J]

Sounds like the sort of thing that could only be confirmed by some advanced algebraic equation. Much beyond my skill. Maybe I'll email progressive and ask their opinion.

[brandEn]

This is a great discussion. In my head it seems like the tighter end should be down and the unsprung weight would be at the top. But ya physics and math ain't my gig man. Haha. I am sure it's fine either way. My biggest concern is getting the correct amount of fluid. I don't want to blow my seals.

[bwaller]

I'll hold my breath and see if I can write down my thoughts before my mind strays....hey did I adjust those power valves on that RZ?

Valve spring progressive winds toward head, fork spring at the top. The fork top should be the constant (cylinder head also) and the wheel does the moving, as does the valve spring retainer.

The progressive winds make contact (probably not with valve springs) after very little movement and become ineffective. If they aren't contributing to the spring load it doesn't make sense to have them moving up & down adding weight to the assembly.

Measure fluid level to the top of the tube with the spring out & the tubes bottomed in the leg. This is an F2? Start at 175mm and adjust according to the amount of travel you end up with. If it bottoms too easily hard on the brakes add equal amounts to each leg until you're happy. Install an o-ring (or zip tie) on one tube to track movement.

[brandEn]

Now that makes sense. Thanks for the post. This project has K8 forks on it though it is a K4.

[tweakin]

Nice updates B, but I am bummed you changed the name. 

[brandEn]

Really? Well I always kept calling it the K4 so it just seemed right. La Flama Blanca is way to hard to say all the time...

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, but does it really matter?! The weaker section would compress first irregardless?

[iron_worker]

There would be a slight change in sprung/unsprung weight as the spring compresses but I think the difference would be quite small when swapping the springs end for end when compared to the weight of the forks themselves and wheel/tire/disc/caliper. I'm thinking unless you're a super sensitive pro track rider then you will never be able to tell the difference.

You would see more difference from slightly varying levels of oil I would think.

IW

[brandEn]

So today was science and physics day in the garage.... ya right.


I am putting an 18" front wheel on this build, replacing the stock 19". Having a smaller front wheel will throw of the reading of the speedometer and odometer because they are calibrated for the larger 19" wheel. It was suggested to me to get a speedo drive from a 400F because they come stock with an 18" front wheel. I was lucky and found one on Ebay in great shape. Its from a 1975 CB400F. The seller on Ebay even had a picture of the bike it came off of so I am "pretty sure" its from a 400F. You know how that goes. Anyway, I took apart the 400F speedo drive and the 750K speedo drive to see if I could find any difference in the gears. I didn't do any measuring but its was pretty obvious there are some differences. First is the part number. The part numbers for a 1975 CB400F and a 1975 CB750K are different so that's the first good sign. Visually comparing the speedo drives side by side they are identical however. The differences lie inside the drives themselves.


The internals upon first inspection look identical





The 750 gear on the right has tighter gearing








Looking from the top you can see the 400F gear has larger teeth





Larger gearing on the 400F here as well





I cleaned everything up and reassembled them with new grease. I used my speedo drive adapter to spin them one complete revolution and measured how far the speedo drive cable turned. The 400f turned about 2 3/4 revolutions and the 750K turned about 2 7/8 revolutions. I am guessing thats all it takes to make the difference in calibration. Hopefully and I am right and my speedometer will read correctly.







Any comment's, criticism, and experience on my methods here are welcome.

[flybox1]

nice pictures and investigation. small details, big difference.
this will surely help someone else out in the future.

[brandEn]

Thanks, I hope it can help someone... especially me!