Author Topic: CB750 Racing (Read 32912 times)

bwaller · « **Reply #75 on:** May 03, 2015, 03:49:18 AM »

1" up or down = 1 degree for 55.5" wheelbase. Ballpark boys.

Haybus · « **Reply #76 on:** May 03, 2015, 12:49:32 PM »

I converted the 2.0" extensions to 1.25". Below are my options I've calculated. Looks like all the extenders are viable with the new 45mm offset triples. Probably even better with 30mm offset triples. I'll get started on those after I get the new triples are fitted. Probably harvest the stem from the stock setup.

Alan

Haybus · « **Reply #77 on:** May 03, 2015, 12:54:13 PM »

My calculation in case you're interested. 12.125 is the height to the center of the front axle.

turboguzzi · « **Reply #78 on:** May 03, 2015, 01:13:35 PM »

ok, but dont forget that with such an angled swingarm you will run into chain slack problems, or rather big diference between slack in full extended to ful compressed. the only way to solve them properly is to install a tensioner teflon wheel under the bottom run, have it in both my racers. i use one from UFO intended for MXers

Retro Rocket · « **Reply #79 on:** May 03, 2015, 02:53:07 PM »

Quote from: Haybus on May 03, 2015, 12:49:32 PM

I converted the 2.0" extensions to 1.25". Below are my options I've calculated. Looks like all the extenders are viable with the new 45mm offset triples. Probably even better with 30mm offset triples. I'll get started on those after I get the new triples are fitted. Probably harvest the stem from the stock setup.

Alan

What is your rake now Alan...? Just remember, going from 45mm to 30mm is a massive jump, they say Mick Doohan could tell 1mm difference in offset, I know your not Mick, but you get my point, try stick somewhere near 4 inches {100mm} of trail, the higher the number for trail, the less the bike wants to turn in, the smaller 18 inch wheel helps turn is too, you can get to a point where the trail fights the wheel, this gives the feeling of the bike wanting to fall into corners all of a sudden, this is usually the result of too much trail.... Its quite a fine balance. PM me your email address and i'll send you the trail converter...

bwaller · « **Reply #80 on:** May 03, 2015, 05:12:33 PM »

TG is right, and that's another one of those "next" jobs. No such thing as one change to a chassis! The 750 swingarm is even shorter than mine so I expect the need for a chain guide is even greater. One negative about picking up the rear is creating a poor arm angle and the need for enough chain slack.

John, what have you done to address this?

Haybus · « **Reply #81 on:** May 03, 2015, 06:20:32 PM »

I haven't really changed anything at this point, other than the 18" front wheel. As shown in the picture I attached, baseline rake is 26.8 degrees and trail is 3.48". It felt really heavy in the corners, like it was trying to push through the corner. My friend who blew up his motor was corner working the first race weekend and he mentioned it looked like I was struggling to get the bike to turn as well. I get the point I need to make small changes. That's what I'm preparing for with the extensions and different triples. I could certainly leave well enough alone and just ride it like it is for the season. But what would I do with all my free time?

I won't make the 30mm offset triples until I see how the 45mm work out.

I noticed a difference in chain slack when I was installing all the extensions to take the rake measurements. No worries making a chain tensioner, but I'm only at -7 degrees with the 1" extensions, which is the same angle as my modern bikes. I'll be checking it out closely for sure, but I do have the stiffest springs Works puts on shocks.

Alan

Retro Rocket · « **Reply #82 on:** May 03, 2015, 06:29:02 PM »

Alan, its hard to compare to modern bikes as the swingarm pivot will be in a completely different place to the old 750, you'll also notice a lot of modern bikes also have a delrin or teflon type chain guide screwed to the front top of the swingarm, actually, one member i have seen has a delrin strip at the top front of the swingarm to stop the chain directly riding on the arm, if i can find the pic i'll post it here...

JohnN · « **Reply #83 on:** May 03, 2015, 06:45:30 PM »

I have a tensioner that I am trying to install but the exhaust is in the way, so I would like to see how others have solved this problem. I have to leave extra slack in the chain to compensate. This setup is from late 2013, and it has allowed the chain to bounce off the top of the swingarm pivot- just another problem that needs to be solved!
John

Retro Rocket · « **Reply #84 on:** May 03, 2015, 07:09:43 PM »

Here's that arm i was talking about, the screws are countersunk {obviously} ....

bwaller · « **Reply #85 on:** May 03, 2015, 07:14:45 PM »

That's the same arm I have now. It may be the 750 pivot is slightly lower than the 500/550 not sure. Here's a picture of the guide I made with a piece of Delrin as sliding material. This is before the new swingarm.

JohnN · « **Reply #86 on:** May 03, 2015, 07:38:17 PM »

Thanks to both of you for the photo's- I think I'll scrap the spring roller idea and add the slides.

Alan- the changes you are trying first won't get you in trouble and it may help. Try it at the Ridge this month, which is more flowing and does not have as many slow/tight corners as Pacific. Did you encounter any wobbles or tank slappers last weekend? Round 4 at Pacific will be a good test for overall stability now that your engine is running better which will equate to more speed at turn 1. My past problems were worst on the faster corners.
John

Retro Rocket · « **Reply #87 on:** May 03, 2015, 08:46:19 PM »

I forgot to ask, are you guys all running steering dampers...?

JohnN · « **Reply #88 on:** May 03, 2015, 09:17:43 PM »

I am, currently set at 3 of 6 clicks.

Haybus · « **Reply #89 on:** May 03, 2015, 10:57:48 PM »

No tank slappers or misbehaving when it was running properly. But I don't think I was really pushing to the point I would notice problems. I am a novice after all

. It feels pretty solid, other than turning like a tank. I don't have a steering damper yet, but I didn't feel like it needed one. I'm sure that will change after I start messing with stuff, along with a whole host of other problems I'll encounter.

Alan

Retro Rocket · « **Reply #90 on:** May 04, 2015, 01:33:43 AM »

Quote from: Haybus on May 03, 2015, 10:57:48 PM

No tank slappers or misbehaving when it was running properly. But I don't think I was really pushing to the point I would notice problems. I am a novice after all . It feels pretty solid, other than turning like a tank. I don't have a steering damper yet, but I didn't feel like it needed one. I'm sure that will change after I start messing with stuff, along with a whole host of other problems I'll encounter.

Alan

Alan, I used to ride these bikes quite hard , {young and stupid

}, I'm sure you are riding harder on the track than I used to on the street {well I hope you are

} and I always fit a damper on these old Honda's {k models}, I've had some very nice handling ones and still had some mean tank slappers, never had a tank slapper with a damper fitted though. These old girls originally didn't have a lot of trail, hitting bumps at speed could start a wobble any time and its scary as hell, a damper is great insurance and gives the steering a nice, sure footed feel... I'm sure thats why Honda changed the rake and offset on the F models {28 degrees and 50mm offset},adding about 18mm of trail which added stability.. You may also notice that Honda added a threaded hole on the bottom triple clamp specifically for a steering damper.

turboguzzi · « **Reply #91 on:** May 04, 2015, 04:23:46 PM »

Quote from: Retro Rocket on May 03, 2015, 06:29:02 PM

Alan, its hard to compare to modern bikes as the swingarm pivot will be in a completely different place to the old 750, you'll also notice a lot of modern bikes also have a delrin or teflon type chain guide screwed to the front top of the swingarm, actually, one member i have seen has a delrin strip at the top front of the swingarm to stop the chain directly riding on the arm, if i can find the pic i'll post it here...

+1
the position of the sprocket in relationship with pivot height is what you change when you angle the arm more. modern bikes sprocket postion are designed for those higher angles, our CBs not... will take a snap of the roller in my gpz

creepxstreet · « **Reply #92 on:** May 05, 2015, 06:09:40 AM »

Lots of excellent info in these posts, I really enjoy reading them. Is there any solid info online about suspension theory and design in general for motorcycles? Like not model specific, but how everything is related?

Also, who makes those frame sliders?

Old Scrambler · « **Reply #93 on:** May 05, 2015, 06:43:11 AM »

You can shape your own material (hardware store)............buy new sliders designed for MX bikes..........or 'borrow' the slides from used MX and Dual-Sport bikes.

Rocketman · « **Reply #94 on:** May 05, 2015, 12:28:02 PM »

McMaster-Carr is a great source for materials, fasteners, supplies, etc., including delrin. They even had an o-ring for my oil pump that is no longer available from Honda.

Retro Rocket · « **Reply #95 on:** May 05, 2015, 04:59:16 PM »

Quote from: creepxstreet on May 05, 2015, 06:09:40 AM

Lots of excellent info in these posts, I really enjoy reading them. Is there any solid info online about suspension theory and design in general for motorcycles? Like not model specific, but how everything is related?

This guy has a lot of knowledge on frame and suspension theory but its a pay site...

http://www.tonyfoale.com/

Haybus · « **Reply #96 on:** May 05, 2015, 07:55:43 PM »

I wouldn't mind reading a book about suspensions, probably lots of useful information. Anybody read Tony Foale's or Paul Thede / Lee Parks' suspension books?

creepxstreet · « **Reply #97 on:** May 06, 2015, 08:05:32 PM »

Quote from: Retro Rocket on May 05, 2015, 04:59:16 PM

This guy has a lot of knowledge on frame and suspension theory but its a pay site...

http://www.tonyfoale.com/

exactly what i was looking for. theres a bunch of free articles too with good info

Haybus · « **Reply #98 on:** May 10, 2015, 11:29:57 AM »

Got my new triples installed and my damper fitted up. With the 1" shock extensions that brings my rake down to 24.9 degrees and my trail up to 3.68". I can drop up to another 1 degree of rake and only go down to 3.41" trail. I think I'm in business to play with some settings now, after some track time of course. Also had to make new steering stops. Was going to drill and tap into the stops on the lower triple, but John gave me a better suggestion. The damper attaches to the frame with a clamp and then I made a bronze bushing that goes through one of the larger holes in the triple.

Alan

Old Scrambler · « **Reply #99 on:** May 10, 2015, 11:56:28 AM »

Nice Stops...............I like the rubber tips and the pin lanyard

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Author Topic: CB750 Racing (Read 32912 times)