Author Topic: CB 750 Project 1 - Rides Well but a few tweaks needed (Read 113471 times)

timbo750 · « **Reply #750 on:** November 15, 2016, 08:11:52 PM »

Quote from: madmtnmotors on November 15, 2016, 10:47:57 AM

disco is referring to the "caps" or "boots" that would be the hard plastic resistor boots that were used with the stock coils, but since you are running Dyna coils you would not likely be using these if you are using Dyna wires.

I should really read things more carefully before I respond.

timbo750 · « **Reply #751 on:** November 15, 2016, 08:15:03 PM »

I was thing of trying another set of carbs. I have a set that looked quite clean on the outside but after removing the bowls and finding dried up and calcified old fuel I have realised that will be more work than it's worth. And to top it the main jets were #130.

scottly · « **Reply #752 on:** November 15, 2016, 08:33:59 PM »

Quote from: timbo750 on November 15, 2016, 01:31:04 AM

Dyna S is in. Its still not running on 4 cylinders this time 1&2 exhausts are getting hot and 3&4 are cold. Exhaust fumes are heavily laden with unburnt fuel.

Try swapping the #3 and 4 spark plug wires.

timbo750 · « **Reply #753 on:** November 15, 2016, 09:02:32 PM »

Here is something I tried but not sure if it means anything.

I put my hand over number 4 carb to see if the revs changed, they didn't, but when I removed my hand it had a lot of fuel on it and then the revs went up as though #4 was firing. Did the same for all other carbs. #1 stalled quickly, #2 wanted to stall and #3 behaved like #4?

I haven't benched synced again yet but they all look to be within 1mm of each other, can that 1mm make that much of a difference?

timbo750 · « **Reply #754 on:** November 15, 2016, 09:33:01 PM »

Quote from: scottly on November 15, 2016, 08:33:59 PM

Quote from: timbo750 on November 15, 2016, 01:31:04 AM
Dyna S is in. Its still not running on 4 cylinders this time 1&2 exhausts are getting hot and 3&4 are cold. Exhaust fumes are heavily laden with unburnt fuel.
Try swapping the #3 and 4 spark plug wires.

Tried that, made no difference. Then I swapped leads between 1-4 and 2-3, now we have a more temp across the exhausts and definitely less unburnt fuel out the exhaust. I was actually not expecting much change.

timbo750 · « **Reply #755 on:** November 15, 2016, 11:51:51 PM »

I let it sit for a couple of hours and started nicely, it idled ok, a bit rough but I am certain the sync is out.
I let it idle for a while to let it warm up and exhaust temp. Everything seemed to warmi g a nice slow rate until it started to idle a bit rougher and then 1-2 exhaust warmed right up and 3-4 stayed cool.

timbo750 · « **Reply #756 on:** November 16, 2016, 11:51:19 PM »

Pulled the carbs to bench sync again - the proper way, before I did I ran the engine with fuel tap off to drain the carby bowls a bit.
Carbdy 4 was empty, it has the coldest exhaust when running.
Carby 3 had half a bowl and 1&2 were almost full.
No I need to work out if 4 is too rich or the others too lean.

Terry in Australia · « **Reply #757 on:** November 17, 2016, 01:16:44 AM »

It's definitely your carbs Tim, did you say you have another set? If not, I've got some spares that you can try. Cheers, Terry.

timbo750 · « **Reply #758 on:** November 17, 2016, 01:43:53 AM »

Terry, I just reset the floats and changed the jet needles to second from the top. Will refit tomorrow and try again. I have been thinking about asking if you could sync carbs and maybe putting it on a trailer and seeing what magic you can weave.

Terry in Australia · « **Reply #759 on:** November 17, 2016, 05:15:05 AM »

G'Day Tim, as much as I'd love to, I'm not home long enough to get any work done on my own bikes, let alone anyone else. This week for instance, I'm driving from Canberra to Bairnsdale to visit my old Ma today, (450 Km) then on Saturday up early to drive home to Melbourne (320 Km) then leave Sunday just before lunch for the return drive to Canberra. (680 Km) Still, my offer for a loan of a set of carbs stands mate. Cheers, Terry.

timbo750 · « **Reply #760 on:** November 17, 2016, 10:05:39 AM »

Thanks Terry. Can you recommend anyone who can sync them for me.

Terry in Australia · « **Reply #761 on:** November 17, 2016, 04:31:18 PM »

Yep, take it to Jeff at Ace Motorcycles in Aileen St, West Heidelberg, tell him I sent you, the idle circuits are blocked, leave them on the bike and he'll tune it for you while he's at it. He's an "old school" mechanic so he'll sort it out for you. He can also do your roadworthy. His number is 94572723. Cheers, Terry.

timbo750 · « **Reply #762 on:** November 17, 2016, 05:47:26 PM »

Terry, thanks. I will give him a call later.

timbo750 · « **Reply #763 on:** November 18, 2016, 06:07:14 PM »

Terry, thanks for the contact. He can do something in about a week. All I need to do now is fit everything off.

Safe driving. Canberra to Bairnsdale - was that via omeo? You doing it on 2 wheels or 4.

timbo750 · « **Reply #764 on:** November 18, 2016, 08:42:46 PM »

Checked all the idle jets and they were blocked, when I changed out the non genuine for the genuine I must of forgotten to check. I also got the bench sync for more accurate and two of the float heights were a bit off.

It now starts a bit better idles better and responds to throttle better. The return to is still not right and definitely needs a proper sync but at least it doesn't idle like a harley.

Now I just need to fit the last few things and get to the mechanic for fine tuning and a roadworthy.

Terry in Australia · « **Reply #765 on:** November 18, 2016, 09:40:40 PM »

Hey my Harley idles very nicely Tim, please don't compare it to that old sewing machine thanks!

timbo750 · « **Reply #766 on:** November 18, 2016, 10:11:06 PM »

Yeah, not trying offend. But an inline 4 should smoother than v twin - in theory that is.

Terry in Australia · « **Reply #767 on:** November 18, 2016, 10:57:02 PM »

Ha ha, yeah, my three V twins (well technically the two VTR1000's are 90 degree "L" twins, as opposed to my 60 degree Sportster V twin) are actually very smooth at idle Tim, but the "sewing machine" comment really describes how smoothly an "across the frame 4" should idle. Good to see yours is getting better, they really are a simple device, so not hard to get 'em running right. Cheers, Terry.

timbo750 · « **Reply #768 on:** November 19, 2016, 01:32:19 PM »

Having never riden a twin other than my brothers yamaha 650 cruiser thing (cant remember the model) my only other experience is sitting next to a few spine shakers at the lights.

Terry in Australia · « **Reply #769 on:** November 19, 2016, 02:39:16 PM »

Quote from: timbo750 on November 18, 2016, 06:07:14 PM

Terry, thanks for the contact. He can do something in about a week. All I need to do now is fit everything off.

Safe driving. Canberra to Bairnsdale - was that via omeo? You doing it on 2 wheels or 4.

No worries Tim, no, I'm in in the car this trip, I drove from Canberra to Bairnsdale via Cooma, Bombala, Cann River, then from Bairnsdale to Melbourne yesterday, and back to Canberra later this morning. The car is fantastic, a new (well it was new when I leased it in October last year) Ford Territory turbo diesel, I filled it up in Canberra and I'll need to fill it again this morning as it's down to "200 Km to empty", but that's not bad considering it's already done 780 Km, and it's only got a 75 litre tank. That's around 36 MPG, or roughly the same consumption I get from my CB750.........

timbo750 · « **Reply #770 on:** November 19, 2016, 04:24:44 PM »

That is good mileage, my cruiser uses about 13l/100 around town and about 12 on the highway. Goes up to 18 on the highway when towing though but probably weighs a ton more than territory.

timbo750 · « **Reply #771 on:** November 19, 2016, 08:07:52 PM »

Front and rear guards fitted. Tail light is not working. I think I fried the circuit with the wtong polarity but being led it should have diode protection. Unfortunately bought it too long ago to claim a replacement so a new one has been ordered. Also had to order mirrors, there is always something I forget.

timbo750 · « **Reply #772 on:** November 19, 2016, 09:58:10 PM »

I am on the home straight now.
Tank and side covers now fitted, just need badges on the side covers. My centre stand is resting on the chain and interfering with the pillion pegs, I always thought that it might not be the right one, now I know for sure so its coming off for now.

All I need to do now is fix the tail light and fit the mirrors.

Terry in Australia · « **Reply #773 on:** November 20, 2016, 03:10:42 AM »

That looks great Tim, well done! Your centre stand probably is the correct one, it's just that when the OEM 4 into 4 pipes are fitted, they stop the stand from hitting the chain, so when you use a 4 into 1, you need to fabricate a "stop", which is usually just a short length of flat bar with a hole drilled in it at one end, the bolt for the pillion footpeg goes thru the hole and the other end of the bar stops the centre stand "foot" from hitting the chain. Or, you can screw a piece of plastic to the foot of the stand, and use it for a chain tensioner. (don't try that, it doesn't work very well, don't ask me how I know.........) Cheers, Terry.

timbo750 · « **Reply #774 on:** November 20, 2016, 11:56:43 AM »

I think I will just leave the centre stand off for now. the piece that you put your foot on to lower it and raise the bike is right up against the pillion peg, it's either off an F or a different bike, there is no way it would work with standard exhaust. I have another one and it has clearly been used as chain tensioner, it may need some repair before it gets used.

For now though I have another issue added to the list, the drain plug on #1 carb was leaking, it was also seized and broke when trying to remove it.

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Author Topic: CB 750 Project 1 - Rides Well but a few tweaks needed (Read 113471 times)