Author Topic: CB750 K3F - AKA The Red (Read 122074 times)

70CB750 · « **Reply #325 on:** April 24, 2015, 04:10:30 AM »

With engine off, I can get it to all 5 gears. It involves some wheel rocking.

But on the road it only has 1 and 2, never goes to 3rd.

Kickstart · « **Reply #326 on:** April 26, 2015, 07:15:10 PM »

Argh... sorry to hear that Prokop.

Does it make any noise when you try to go into third, like a clunking or clattering noise?

I had to open my engine back up... I threw together this upside down stand, that worked out nicely.
http://forums.sohc4.net/index.php/topic,107713.msg1642736.html#msg1642736
It made it a easier to flip the engine over (still had my son help), and I was able to access both sides while it was upside down so I didn't have to flip back over to bolt the fasteners on the top half when putting the cases back together.

70CB750 · « **Reply #327 on:** April 27, 2015, 02:45:43 AM »

That's a neat idea, Chris, thank you.

No it makes no noise, the lever just stops dead and what it seems little short of actually shifting.

turkey4me · « **Reply #328 on:** April 27, 2015, 06:26:44 AM »

If you need any parts, I have an F3 bottom end that I'm parting out. Hopefully you sort out your gearing.

70CB750 · « **Reply #329 on:** April 27, 2015, 06:37:09 AM »

Quote from: turkey4me on April 27, 2015, 06:26:44 AM

If you need any parts, I have an F3 bottom end that I'm parting out. Hopefully you sort out your gearing.

I will take any of these parts:

I still believe it is in the shifting mechanism somewhere.

Thanks!

70CB750 · « **Reply #330 on:** April 30, 2015, 04:03:11 AM »

I cleaned and polished all the shifting linkage, it made no difference.

On the positive side, she is charging when she runs.

I will need to pull the engine, there must be something wrong.

MoMo · « **Reply #331 on:** April 30, 2015, 02:39:58 PM »

^

I have not touched my Red Rider 750 with the F motor because of a shifting problem in 4th gear

Good luck with it Prokop

70CB750 · « **Reply #332 on:** May 03, 2015, 08:37:04 AM »

There she is. Double o-rings under neutral switch solved the shifting problems and she shifts like new.

seanbarney41 · « **Reply #333 on:** May 03, 2015, 09:15:55 AM »

Glad to hear you figured it out. Bike looks good...how about some more pics.

Stev-o · « **Reply #334 on:** May 03, 2015, 09:56:52 AM »

Looks great, good to hear shes a shifter. Nomming you for BOTM....

SOHC4 Cafe Racer Fan · « **Reply #335 on:** May 03, 2015, 11:39:53 AM »

Seconded. Please post your acceptance of the nomination in the BOTM Nomination thread:

http://forums.sohc4.net/index.php/topic,147381.0.html

70CB750 · « **Reply #336 on:** May 03, 2015, 01:15:41 PM »

Quote from: Stev-o on May 03, 2015, 09:56:52 AM

Looks great, good to hear shes a shifter. Nomming you for BOTM....

I am honored, Stev-o, but Comstars and BOTM? LOL!

Anyway, accepted. Will have detail pictures and a story in few days.

Stev-o · « **Reply #337 on:** May 03, 2015, 02:24:13 PM »

Quote from: 70CB750 on May 03, 2015, 01:15:41 PM

Quote from: Stev-o on May 03, 2015, 09:56:52 AM
Looks great, good to hear shes a shifter. Nomming you for BOTM....

I am honored, Stev-o, but Comstars and BOTM? LOL!

Hey, ya never know?! Black rims have won and Sam hated them!

SOHC4 Cafe Racer Fan · « **Reply #338 on:** May 03, 2015, 06:33:46 PM »

Not all Comstars are bad. I confess they've grown on me a little over the years. Still haven't put any on a bike.

Retro Rocket · « **Reply #339 on:** May 03, 2015, 06:40:07 PM »

Quote from: CB750 Cafe Racer Fan on May 03, 2015, 06:33:46 PM

Not all Comstars are bad. I confess they've grown on me a little over the years. Still haven't put any on a bike.

I like the boomerang comstars we got on the boldor series bikes...

SOHC4 Cafe Racer Fan · « **Reply #340 on:** May 03, 2015, 06:41:23 PM »

The reverse Comstars are better than ok. I like the wheels on this bike.

Kickstart · « **Reply #341 on:** May 03, 2015, 07:39:18 PM »

Great news!

Looking great... I like the way the comstars look on your bike.

Just curious... how did the double o-rings on the neutral switch cause the shifting problem... and was the neutral light always on?

70CB750 · « **Reply #342 on:** May 04, 2015, 02:55:57 AM »

Quote from: Kickstart on May 03, 2015, 07:39:18 PM

Great news!

Looking great... I like the way the comstars look on your bike.

Just curious... how did the double o-rings on the neutral switch cause the shifting problem... and was the neutral light always on?

The double O-ring actually allowed me to shift all the way up and down and smoothly. It tells me the problem is somewhere around the switch seating, but the shifting forks are - as far as I dare to say - okay.

Will try different switch now.

MoMo · « **Reply #343 on:** May 04, 2015, 05:08:12 AM »

You think the switch was down too far and binding against the drum? Extra O-ring raised it enough to prevent that? Interesting fix, may try the same on the F engine in my K4...Larry

70CB750 · « **Reply #344 on:** May 04, 2015, 05:24:52 AM »

Quote from: MoMo on May 04, 2015, 05:08:12 AM

You think the switch was down too far and binding against the drum? Extra O-ring raised it enough to prevent that? Interesting fix, may try the same on the F engine in my K4...Larry

I suspect the shoulder of the switch against the drum groove edges, just dragging little bit.

But I polished the switch and gthere was no witness mark on it.

MoMo · « **Reply #345 on:** May 04, 2015, 12:07:53 PM »

Quote from: 70CB750 on May 04, 2015, 05:24:52 AM

Quote from: MoMo on May 04, 2015, 05:08:12 AM
You think the switch was down too far and binding against the drum? Extra O-ring raised it enough to prevent that? Interesting fix, may try the same on the F engine in my K4...Larry

I suspect the shoulder of the switch against the drum groove edges, just dragging little bit.

But I polished the switch and gthere was no witness mark on it.

Very strange, your problem was all the time right? My 4th gear problem is only when hot.

Kickstart · « **Reply #346 on:** May 06, 2015, 03:37:39 PM »

Quote from: 70CB750 on May 04, 2015, 02:55:57 AM

Quote from: Kickstart on May 03, 2015, 07:39:18 PM
Great news!

Looking great... I like the way the comstars look on your bike.

Just curious... how did the double o-rings on the neutral switch cause the shifting problem... and was the neutral light always on?

The double O-ring actually allowed me to shift all the way up and down and smoothly. It tells me the problem is somewhere around the switch seating, but the shifting forks are - as far as I dare to say - okay.

Will try different switch now.

Oh... I read that wrong... the double o-ring solved the problem... interesting.

Was it an aftermarket neutral switch?

Does your neutral switch go on and off correctly after adding the extra O-ring?

70CB750 · « **Reply #347 on:** May 07, 2015, 03:16:19 AM »

It came with the engine, not sure, looks original.

It goes in easy and out too, I have another one coming from Bill Benton.

Will take her out on Saturday again and see what is what.

70CB750 · « **Reply #348 on:** May 09, 2015, 09:53:57 AM »

Put 35 miles on her today, now she shifts with just one o-ring on the neutral switch, seems like once I got her through 1-5 she fixed herself.

The speedo bounces around 60mph, will need to look into it, also the kick stand ďrags in left turns, need to tuck it in more.

Unlike the K0, that has significant kick at 4000 rpms, she pulls steady and without surprise from 1000 up. Did not push her over 5000 rpms, new rings and such, she seems to be happy there - 1000 higher than K0. Up hill in 5th there seems to be a hole, I may eventually go to 125 main jets.

The K0 pulls from stop like tractor, K3F needs more gas and clutch work.

She has an F3 cam advanced 4.5 degrees against original to bring the power band lower.

Overall, happy and pleased, hopefully I did not jinxed her.

Kickstart · « **Reply #349 on:** May 09, 2015, 10:42:19 PM »

Awesome!

Glad to hear the bike is feeling good through the shakedown/beak-in phase.

I wonder if the drum was just hanging up on some kind of debris that got in there during the build, and messing with the neutral switch moved things around enough to dislodge whatever was causing the problem.

Hopefully it's smooth sailing from here.

- Chris

News:

Author Topic: CB750 K3F - AKA The Red (Read 122074 times)