Author Topic: lowering a cb750 i know its been covered (Read 8187 times)

romerider153 · « **on:** May 29, 2012, 11:56:50 AM »

I was looking around for options on decreasing the amount to fork tube sticking up through the tree i need to lose about 2.5 inchs i really dont want to pay for shorter tubes.

I found this thread: http://forums.sohc4.net/index.php?topic=69747.25 and was considering the spacer option . I have two question one does adding a 2" spacer like in the honda chopper link lower the bike two inchs total because in the side by side comparision it doesnt look to be 2" shorter. Second question is what is the max you would want to lower your bike with this method beofer the bike handles like crap. Also down the road id like to get the cyclex air shock tops and some nice progresive springs does lowering this way eliminate those options? Thank you guys

romerider153 · « **Reply #1 on:** May 30, 2012, 06:40:48 AM »

nobody?

Really? · « **Reply #2 on:** May 30, 2012, 06:44:04 AM »

When you said that, I had nothing to offer.

Quote

I was looking around for options on decreasing the amount to fork tube sticking up through the tree i need to lose about 2.5 inchs i really dont want to pay for shorter tubes.

romerider153 · « **Reply #3 on:** May 30, 2012, 11:59:50 AM »

whats wrong with wanting to spend the money elsewhere if the same thing can be achieved for cheaper if nothing else turning them down on a lathe and having them rethreaded would probably be cheaper.

Really? · « **Reply #4 on:** May 30, 2012, 12:15:27 PM »

I wasn't saying anything was wrong, I just had nothing else to offer is all. And, no one else was answering. I didn't think $149 for new tubes was a bad price really. The top of many tubes are rusted and pitted where the headlight ears covered them, the new ones, well you know...

Retro Rocket · « **Reply #5 on:** May 30, 2012, 03:23:28 PM »

Unless drag racing, lowering a 750 isn't a performance mod, quite the opposite, this thread should be in the SOHC section....

754 · « **Reply #6 on:** May 30, 2012, 10:19:16 PM »

I cut tubes down for around 50-70 bux up here, got to be someone down south does them.
Not a performance mod?

??////// Try getting good holeshots with an up in the air bike..On a slammed bike you can launch as hard as you feel like, and it will get up and go..straight..

Retro Rocket · « **Reply #7 on:** May 30, 2012, 10:28:32 PM »

Quote from: 754 on May 30, 2012, 10:19:16 PM

I ct tubes down for around 5-70 bux up here, got to be someone down south does them.
Not a performance mod???////// Try getting good holeshots with an up in the air bike..On a slammed bike you can launch as hard as you feel like, and it will get up and go..straight..

He didn't say anything about drag racing Frank, but if you read all of my post i did.... On the street lowering is the furthest thing from a performance mod that i can think off... I can only think of a couple of things from drag racing that would be any good on the street and they are engine mods, nothing you do to the suspension for drag racing is any good on the street, Street performance Frank, street performance.

romerider153 · « **Reply #8 on:** May 31, 2012, 05:46:46 AM »

so would you recomend cutting tubes instead of the spacers?

Doctor_D · « **Reply #9 on:** May 31, 2012, 07:06:46 AM »

You can use spacers inside the fork tube, below the top out spring. It will bottom out more easily, and you will need to increase the spring rate and damping to compensate. So, while you're in there, weld up one of the rebound ports on the damper tube, and cut the spring down 1" and add a 2" pvc spacer. From there, dial in the volume and weight of your fork oil. Those are cheap ways to increase spring rate and damping.

You need to do your rake and trail calculations based on your final configuration, but the bike is likely to want a steering damper when all is said and done. Oh, and how are your steering stem bearings?

754 · « **Reply #10 on:** May 31, 2012, 07:35:03 AM »

i never tried the spacers, But I think it goes like this ...(hypothetical figures)
Your fork has 4.5 inches travel, you install 2 inch spacer, now you have 2.5 inches travel.. is that correct..
Probably OK for a lot of slammed bikes.

Doctor_D · « **Reply #11 on:** May 31, 2012, 09:23:38 AM »

Quote from: 754 on May 31, 2012, 07:35:03 AM

i never tried the spacers, But I think it goes like this ...(hypothetical figures)
Your fork has 4.5 inches travel, you install 2 inch spacer, now you have 2.5 inches travel.. is that correct..

Yes, that's correct.

754 · « **Reply #12 on:** May 31, 2012, 09:28:59 AM »

For those that have not noticed the High-Po thread has lots of dragracing content, and modding chassis to so, is very relevant. IMO..

romerider153 · « **Reply #13 on:** May 31, 2012, 10:17:20 AM »

the stem bearings are in good shape i was planing on a dampener already so thats no issue. So from what i gather a 2 inch spacer equates to a 2 inch drop? If you go the cut tube method and cut the spring to match you would keep the same amount of travel and relativly stock feel?

Doctor_D · « **Reply #14 on:** May 31, 2012, 10:57:38 AM »

CB's are undersprung in general, so cutting the springs a half inch more than you cut the tubes and putting in a one-inch spacer is highly recommended. Modifying the damper will also improve road feel and handling.

romerider153 · « **Reply #15 on:** May 31, 2012, 11:03:31 AM »

ok cutting the springs a half inch more then the tubes and then 1" spacer is your adding about half " inch more preload on the spring in total all said and done correct?

Eddie · « **Reply #16 on:** May 31, 2012, 12:58:33 PM »

I lowered my 550 1" in the front and when you push the forks down hard the wheel gets pretty close to the motor....cant imagine how close 2" will be..

Really? · « **Reply #17 on:** May 31, 2012, 01:02:00 PM »

I am at about 3 inches

romerider153 · « **Reply #18 on:** May 31, 2012, 01:13:13 PM »

i have my fork tubes slide up about 3 inchs i hate the way it looks hence why im asking about this but tire cleaarance is good . "Really" how do you go about lowering and how does the bike ride?

Really? · « **Reply #19 on:** May 31, 2012, 01:24:32 PM »

I am running shorter CycleX tubes and slid up the tree 1 1/4. 15wt fork oil. The ride is a little bumpy but not bad at all to me. I have not bottomed the fender into the pipes. The whole bike rides good.

romerider153 · « **Reply #20 on:** May 31, 2012, 02:27:34 PM »

what 2" shorter tubes? and did you cut the spring to match?

Retro Rocket · « **Reply #21 on:** May 31, 2012, 02:40:43 PM »

Quote from: 754 on May 31, 2012, 09:28:59 AM

For those that have not noticed the High-Po thread has lots of dragracing content, and modding chassis to so, is very relevant. IMO..

If you are drag racing Frank, this guy isn't....

Really? · « **Reply #22 on:** May 31, 2012, 02:55:09 PM »

The springs were actually short. I thought I was going to have to cut them. There was anice thunk in the front end before I changed the tubes. Gone afterwards.

They have -3's.

romerider153 · « **Reply #23 on:** May 31, 2012, 03:21:38 PM »

yea i know mine ir in great shape tho i just cant justify spending 150 onsomething i can do for free or alot cheaper

Really? · « **Reply #24 on:** May 31, 2012, 03:32:30 PM »

understood. The tops of mine were pitted really bad so it was in the cards to replace anyway.

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Author Topic: lowering a cb750 i know its been covered (Read 8187 times)