Topic: Andys CB810 K2 -updated 14 Oct 2024 - missing link!

[bwaller]

Yea, that is just absolute #$%* luck.

All's well that ends well boys.

[andy750]

It certainly was a project. the first head I used had an invisible crack in the #4 area. It would spew oil after warming up. Bottom line was one head with porting, guides, VJ and surfacing etc that ended up in the junk pile. Plus there was pulling the engine to try and fix it, putting back together (cam timing etc) and it still leaked. Take another head...port, VJ, paint etc etc and reassemble. that frame worked extremely well allowing total access for a top end rebuild. I'll admit I was frustrated but it all came together in the end.

Thanks Mike for finishing it up! It certainly has been a journey..one slick oil pouring one! Anyway lets hope the oil stays inside this time...once the new boots arrive the tuning can take place and Ill get it on the dyno...but with the cold weather upon us dont expect it too soon...Ill try my best .

Kudos to Mike!!

Thanks for all the comments
Andy

[MRieck]

Yea, that is just absolute #$%* luck.

All's well that ends well boys.

That is what I told Andy, Brent. I've had my share of stuff that doesn't go right and it would pay for a few nice vacations in Europe by now. It happens with new stuff....forget about parts 40 years old!

[MRieck]

Oh, BTW....I found out Andy's middle initials are "BP". I knew it!!!!!!

[srook]

Andy,
one of the things that I did to my carbs to fix my hanging idle was to get brand new slow jets from the Honda dealer.  They were pricey but when I was tuning the carb to fix the idle hang the air jet screws seemed to have little effect on the idle.  I assumed the old slow jets were worn and got some new ones.  John Healy, owner of Coventry Spares and former Triumph dealer, is noted for saying that jets are jets not holes.  After 35 years of use I think my slow jets were more like holes than jets.  With the air screws set to factory settings, new slow jets, and the old carb rubbers my hanging idle went away.  Just my experience with the dreaded hanging idle.
Scott

[andy750]

Hey Scott

Great info and I really appreciate it. In this case I dont think its the slow jets. Here is why...previously we had rebuilt the engine a few months back and got it running with the same carbs (cleaned very well and all parts inspected - new needles and maybe even new jets - i forget now). In any case at the time we synched the carbs and the bike ran great! No hanging idle and very smooth throttle response. Only problem was the engine leaked like a sieve due to an invisible crack in the head  .

Fast forward a few months later and new head, rebuilt engine and bike is now reassembled...carbs put back on without being touched from before...hanging idle. Visually you can see the airbox-carb boots are not making perfect contact. The rubber is a little hard. Seal is likely not perfect. So it looks like it is the rubbers....I have some coming any day now so will be an easy swap to test. One more thing to look at is the cable routing as in my haste on Saturday I routed it slightly differently than last time...will reroute and check this also.

thanks for the suggestion and if these two issues are not the cause Ill check the slow jets next.
cheers
Andy

[andy750]

Saturday 20th - re-routed the throttle cables and this helped the idle issue somewhat. Still has a tendency to creep up at idle but getting there...new boots  have arrived so they`ll be installed next. New Honda tach cable now means I have rpms indicated again. Solved the battery charging issue by swapping my Oregon motorcycle rectifier from the K4 to the K2. The K2 rectifer also test bad for one connection. So now will order another Oregon motorcycle rectifier.

Sunday 21st - bright sunny cold morning - temps 33F (real feel 21F) -wasnt so bad once bundled up (leather jacket/windstopper fleece - this really helps and powerstretch fleece - thin but warm). Went for a 10 mile ride and wow what a difference from last week. Pulls like a freight train from the stop lights and one twist of the throttle when at 35 mph accelerates the bike to 70 mph in no time...and so smooth! Now to synch the carbs and really feel what this bike can do....

Brief summary:
CB750K2 with wiseco 810cc pistons
Megacycle cam (125-65 specs)
New valves/honda valve guides
New rocker arms
Jetting - 40/120
Exhaust - HM300s
Air filter  - stock airbox with stock filter
Tires - BT-45s
Chain -RK O-ring 102 links
Sprockets - 17/48 (Z1 enterprises)
Ignition - Dyna S
Coils - stock
Plugs - Denso Iridiums

Still to do - steering head bearings and swingarm bushings.

cheers
Andy

[MRieck]

Saturday 20th - re-routed the throttle cables and this helped the idle issue somewhat. Still has a tendency to creep up at idle but getting there...new boots  have arrived so they`ll be installed next. New Honda tach cable now means I have rpms indicated again. Solved the battery charging issue by swapping my Oregon motorcycle rectifier from the K4 to the K2. The K2 rectifer also test bad for one connection. So now will order another Oregon motorcycle rectifier.

Sunday 21st - bright sunny cold morning - temps 33F (real feel 21F) -wasnt so bad once bundled up (leather jacket/windstopper fleece - this really helps and powerstretch fleece - thin but warm). Went for a 10 mile ride and wow what a difference from last week. Pulls like a freight train from the stop lights and one twist of the throttle when at 35 mph accelerates the bike to 70 mph in no time...and so smooth! Now to synch the carbs and really feel what this bike can do....

Brief summary:
CB750K2 with wiseco 810cc pistons
Megacycle cam (125-65 specs)
New valves/honda valve guides
New rocker arms
Jetting - 40/120
Exhaust - HM300s
Air filter  - stock airbox with stock filter
Tires - BT-45s
Chain -RK O-ring 102 links
Sprockets - 17/48 (Z1 enterprises)
Ignition - Dyna S
Coils - stock
Plugs - Denso Iridiums

Still to do - steering head bearings and swingarm bushings.

cheers
Andy

The cam is a Dynoman 295...not the Megacycle125-65. Also the head has bronze guides. Just wanted to set the record straight Andy.

[andy750]

I stand corrected . Good to know!

cheers
Andy

[andy750]

SATURDAY 27th November

I got the K2 inspected today...and even though I had just replaced the rectifier to cure the starting problem I had to bump start it this morning to get it going...not a good sign...anyway the bike passed inspection although it was a bit embarrassing with the weak horn due to the weak battery...anyway bumped started it away from the inspection place....

I then made a stupid decision...take the K2 to MotoMkt to their Winter Gear day...I just couldnt resist testing out the 810cc of pure pleasure...and sure enough zipping down I-95/128 in the outside lane with head tucked down, elbows in and stomach on tank doing 90+mph it really felt great  . Rt 2 was a similar blast and everything was going well up until the 3 or 4th stoplight when....bike died! Right at Main Street leading into Concord. I pushed the bike to the side of the road...

A KLR rider passing in the other direction on Main St came back to help and offer moral support..."I used to have a CB like that and they all did that" he said in his English accent...then with a good luck he left and I pushed the bike into a parking lot and tried 4 or 5 times to bump start it...no luck...very weak battery...

I called the g/f...she was having lunch with a friend...I sat there and thought of my options...then recalled that Carlisle was not so far away and Peter (local SOHC rider) might be in! Sure enough he was and I managed to interrupt his glee at buying and fitting new heated Gerbing gloves and temp controller...he was kind enough to offer a variety of solutions and said he would be right round to help.

While waiting I tried one more bump start...it worked and the engine roared into life...I called him back but he had just left...I let the bike idle until he arrived but it was all to no avail as one twist of the throttle and it died....so Peter very kindly let me borrow his Guzzi battery to get home even though this meant no playing with his heated gloves - thank you Peter!!!!

I got home in record time making use of the new battery...picked the VStrom up and went back and delivered the battery back to Peter....and still made MotoMkt

So HUGE thank you to Peter for rescuing me from my own stupidity

much appreciated
Andy

 

[andy750]

and there is more stupidity  .....

SUNDAY 28th November

So....I was impatient.....I recharged the battery in the morning while I was changing the regulator out...it was such a nice sunny day and the twisty road gods were calling me.....D-o-v-e-r (local town reached by twisty country roads).....so at 1.30pm I took battery off charger and put it in the K2 and headed down the VFW to Rt 109 to Dedham Street to Mill Street and stopped for this photo...



I then went to start the bike....aaaarrrrgggghh...nothing!

So I tried several times to bump start it on this small incline..up and down, up and down....nada  



I called Ben (forum member azuredesign) who lived locally .....and he was kind enough to come asap and once again rescue me (see a theme developing here?).

While waiting  for Ben i took these pics of my bike at the side of the road...







Ben came, battery got me home....and then it was straight back to Bens place with his battery on the trusty VStrom . Thank you Ben!!!! Beers are on me at next beer night!!

Rode home  - 37F in Natick, 41F in West Roxbury...stopped for this pic...



Thanks to both Peter and Ben for rescuing me this weekend. next time ill take a spare battery with me! Now to troubleshoot...

cheers
Andy

[Jerry Rxman Griffin aka MuthaF'er]

Andy,

I'm sure you already know this stuff but: Leave your Battery Tender hooked up all the time in your garage and remember that idling will drain it. Mine was pulling maybe 12.8 to 13V max while at highway speeds. I'd drop a gear or 2 at slower speeds to keep the rpms up and volts marginal. I avoid running around town if possible. The turn signals and the beeper are my volt meter. If they slow down I know I might be in for trouble. Remove your headlight fuse during the day too if you need to. In the mean time hook up the volt meter and see what it's doing before venturing out next time. See what it does with the headlight off too. Hell, this could take all winter to chase down. My worst nightmare. No elusive 14.5V for me and I'm running 5ohm coils with the Dyna III and halogen bulb.

Looks like you had nice days otherwise    Oh yeah, no kick starter? Put it back on in the mean time.

[the technological J]

i just had the same prob and it ended up i had the rectifier wires hooked up wrong.. switched them and it runs like a champ

[Zaipai]

Yea Andy your not alone hear, I have the same problem. I have yet to figure out what it is. I am going to try replacing the battery and see if that works since its about the only thing I have not swapped out.

Sorry about your being stalled on the side of the road, tho it sounds like you had fun up to then..

.: Scott :.

[MCRider]

Just a thought, the only time I had such a problem it was the starter button shorting out against the handlebar and draining the battery. Not exactly your problem.

Oh yeah, one other time it was 1/3 of the stator wasn't working, my memory is cloudy on exact details (in both cases), but it required replacement of the stator.

can be frustrating.

[andy750]

Thanks guys for all the feedback and clearly I have some electrical troubleshooting to do. I have one battery recharged and next one goes on tonight so will have a back up for next ride testing once I`ve gone through all the connections with the multimeter. Some great suggestions here to try and Ill update when/if I figure it out.

Jerry - kickstarter no longer works unfortunately. When bottom end was rebuilt years ago the mechanic who did it messed up the kickstarter reinstall and it never worked after that. Really miss it at times like this.

More soon
cheers
Andy

[andy750]

Worked out the problem with the battery not holding charge....with multimeter at hand, changing regulators, rectifiers, comparing with the K4 and calling friends (including MikeR) I worked it out...frayed ground wire going to the alternator...

After checking everything else it was time to pull the gear cover...





check the wires..



and found the problem...note the frayed green wire..





Cant wait to replace it and button this back up..snow is almost here!!

cheers
Andy

[Jerry Rxman Griffin aka MuthaF'er]

Something obvious!! YES!! Glad you found it. Is that the sub-harness? Yamiya has those I do believe if you wanted to replace it.

[MCRider]

Something obvious!! YES!! Glad you found it. Is that the sub-harness? Yamiya has those I do believe if you wanted to replace it.

Yes, glad for Andy that's all it was. I vote for buying the new harness over repair. (Its so easy to spend other people's money.  )

[andy750]

Yes that was the sub harness and just glad it was so easy. Mike R has mentioned he has a spare so looks like I am good for now. Good to know about Yamiya though...maybe Ill take a peak

thanks!
Andy

[andy750]

Update:

The alternator wire was replaced before Christmas. Then winter came and no time for real testing.

This past weekend I replaced the airbox-carb boots, synched the carbs and took it for a good ride. Simply amazing! The 810cc power is there (I rode my stock K4 immediately afterwards and there is definitely a difference). Cruising on the highway at indicated 70mph it will pull effortlessly up to an indicated ton with no instability and still more to give - rpms in the 6 -7K range. High speed is best when sitting way back against the hump, head down, elbows in and really going for it. The sloping corners on the highway are exciting at that speed  .  Dont worry this is not a regular occurrence just a test ride. Really is a fast fun bike. Scarily so! More fine tuning and then dyno run in next few weeks.

More soon.
Andy

[andy750]

This past Saturday I took the K2 to see MikeR to confirm my carb balance was good (it was) and he tweaked the air/fuel screws  - not a whole lot as the plugs were all "perfect" colour. Must have been the high speed run up the Mass pike getting to his place. Nice powerband at 5000 rpm and pulls well after this. Top speed as confirmed by GPS was 95 mph. My K2 speedo is fairly accurate according to the GPS which is amazing for this unfurnished speedo. 

Dyno run tentatively scheduled for 23rd April at Harrys Machine shop Rt 9. This guy is probably the best in New England and knows what he is doing! Looking forward to seeing the numbers...

More soon..
Andy

[Jerry Rxman Griffin aka MuthaF'er]

What numbers are you hoping for?

[andy750]

What numbers are you hoping for?

Ill let the dyno speak for itself

[andy750]

Pre-dyno run today since I had to go into work....bike is running great!

I hit the ton today...recorded by GPS - 104 mph at indicated 6800 rpm (was pretty stable) in top gear (done on a closed course since I dont condone speeding on public roads as that would be irresponsible  ). Stock speedo was surprisingly accurate. 

Pics shows aftermath...




Going home..



Dyno on Saturday...

Andy