This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
Messages - paul_D
Pages: [1]
1
« on: April 20, 2014, 02:56:11 AM »
Oh and compression was good, varied, but high enough. 105psi +
2
« on: April 20, 2014, 02:55:28 AM »
electrical gremlins not getting enough voltage to the coils and faulty charging system. Fixed and fixed.
Found underlying problems. Im fairly certain my needle jets and needles are nolonger mating correctly and the intake rubbers are hard as a rock causing rich middle from the needle and lean conditions from the boots.
Ordered both new intake rubber and needle jet sets. Should bring it right back with a vacuum sync to balance everything nicely.
3
« on: April 01, 2014, 08:50:50 PM »
Fair enough. What would cause low compression when hot? I guess rings, gasket or valves. Not a fan of that idea.
4
« on: April 01, 2014, 08:36:21 PM »
Hi,
Any chance you are loosing compression as the engine warms up? Ken
I have no idea. How would you check? Just the same as when cold?
5
« on: April 01, 2014, 06:15:15 PM »
Yep its incomplete burn. I don't know what's causing it. The ignition is set correctly. Advance is working.
I've exhausted everything I could think of. What you could think of. What other forum searches could bring up.
I took it too an old bike mechanic in hopes he can find something I've missed. Hoping its cheap and simple.
I'll post back with the findings.
6
« on: March 31, 2014, 12:52:09 AM »
Looking back at your original post, I don't understand "main jet set at 100" what is that referring to?
Also, what position are the main needles set to, i.e. the circlip postion on the needle grooves. Usually five grooves with factory setting ordinarily the centre one.
Sorry, main jets were 100's. I've swapped the 100's out for 78's. The carbs are 649a which called for 78 main jets. 627b's had the 100s. The circlip is in the 3rd. Middle clip. Looking back at your original post, I don't understand "main jet set at 100" what is that referring to?
Also, what position are the main needles set to, i.e. the circlip postion on the needle grooves. Usually five grooves with factory setting ordinarily the centre one.
New plugs have a strong spark. The fouled plus have a very small blue/purple spark or none. When I install new clean plugs, each cylinder does fire up and get hot.
7
« on: March 30, 2014, 09:47:36 PM »
coils are new
But I think poor grounding and connections between the charging system, the reg/rec and ultimately the coils.
8
« on: March 30, 2014, 08:41:45 PM »
Can you physically see that any choke influence has been removed when you feel it's off?
I'm not sure I understand your question, I'll answer it two ways. 1st, with the choke applied after start up the bike starts dieing and becoming unresponsive until the choke is in the open position. The bike will not run with choke closed. 2nd, with the carbs off the bike, choke in open position the plates were horizontal and equal. (minimal interference with flow)
9
« on: March 30, 2014, 08:11:51 PM »
I only manage about 1-3 miles before the plugs foul and the bike starts miss firing first at higher rpm and slow miss fires down through the rpm until it dies completely. how does it run when hot?
can you get 8,500 rpm in 4Th?
the standard air cleaner is dry,not oiled.
how is the timing?
is it retarded ??
just a few ideas to check
It fouls when hot. Cant get it up to 4 wide open long enough. Fouls out. Also not road legal right now. The air cleaner is a foam unit. Foam air cleaners use oil to trap dirt and repel water. The timing is spot on with a strobe light. Hi,
As with most 4 to 1 in my day ran as rich as hell.You are going to start from basics float height,every air way clear,smaller jets etc.Go find a nice stretch off road give it full bore hit the kill switch with the clutch in coast to a stop pull the plugs and see what colour they are and adjust as necessary smaller, bigger jets etc.Frackin pain in the arse remember it well also cant remember with the 500 have you got anything blocking the air intake like the 400 vent under the seat?
Cheers
Bitsa
ps Dont know if its me but just once I wish my 750 plugs would look a bit black but they dont with fuels in the 70s lead etc they should look slightly brown impossible today confuses the crap out of me but they are the same colour as my modern xjr1300.
This bike (German/netherlands carburetors) does have the underseat airduct as well as 78 mainjets. The rest of the world had the same carburetors without a duct and 100s. I've tried it both ways, same result. Even tried 78s with no duct, still fouled. Has it just started doing this? was there any changes that are relevant? just rebuilt? not been used etc.
An easy statement would be that it has too little oxygen to burn the fuel......if the jets are normal then you would first look at the air supply.......is the choke completely clear when not used? remove the whole airbox and try it, should run a bit lean in that spec.
As John says, have you verified the timing is normal.
The bike is rebuilt. I have the choke open, I've tried it with the air filter and tool tray removed for the maximal intake. Still rich. I am going to try new plugs again, recheck the timing. And check the voltage drop across the coils. I think the drop is too low, leading to a weak spark that fouls quickly.
10
« on: March 30, 2014, 12:35:28 AM »
Hello
I'll describe my bike setup before the problem.
1972 cb500 (german/ netherland spec.)
649a carburetors
78 main jets
40 slow jets
1.125 turns out air screw
22mm float height (checked with tool and also a clear tube)
original air duct installed
Uni foam air filter (light dusted with K&N air filter oil)
Jardine 4-1 exhaust
d7ea ngk plugs gaped to 0.65mm
The bike starts up well with a little choke (3 degrees celsius today), slowly turn off the choke as it responds. I start riding the bike and when the bike is finally up to operating temperature (2-3 miles) the bike starts back firing/ miss firing and stalls out. Pull the plugs and I get 4 black plugs that are wet with fuel.
I believe the problem is a weak spark, because no matter what I do to the bike on the carb/intake end has any effect. I've had the filter on and off and the results are the same. The main jet set at 100 and the stock 78, no effect. Air screw adjustment does affect off idle performance, thats about it.
Any or all thoughts would be appreciated.
11
« on: March 15, 2014, 12:21:34 PM »
The 500 with 649A carbs (78 main jets) and airbox cover performed equally well as models with the 627B carbs (100 main jets). Top speed in Dutch and German tests prooved 179 km/h. BTW, I never managed more than 170 km/h @ 8500 rpm, but I weigh 90 kg, am 196 cm tall and was not dressed like a test pilot. On the dyno my bike reached the theoretical top speed of 185 km/h @ 9250 rpm.
Many years ago, out of curiosity I tested with 100 main jets and the airbox cover removed on the road. Germans did the same. With standard 4 in 4 exhausts it didn't bring anything but extra intake noise, but feel free to experiment. Needle standard is in 3rd (middle) groove, air screw is one turn out +/- 1/8. Slow jet is 40. Stock paper filter element is best. Float level is 22 mm (but is always right unless somebody messed with them).
But delta I was wondering how your bike runs without the air duct and the 649a carburetors. I am consistently told over on sohc4 that its impossible to run them without it, which seems ridiculous. And what are the measurements of the airduct as a temporary fix ? I am looking for one to fit and try out but cant find one.
12
« on: March 14, 2014, 08:43:02 PM »
Thanks delta. I am asking because I have been trying 100's and no cover on my cb500 with needle in 3rd and air screws out 1 turn with no luck and fouling until it stalls while riding.
I am looking to put the 78's in on my carbs but I don't have the duct assembly. As you know from sohc4.net I am repeatedly told these carbs simply cannot work without the duct. Seems ridiculous to me. I am also told I should give up and use 022A carburetors. I know these 649a's will work. Just want to return to stock as much as possible to eliminate any variables.
By the way I am located in Canada.
And I've even read your posts on Frances sohc board in French about cb500 and 649a's. Was nice to see you consistently use deltarider as your username.
13
« on: March 14, 2014, 08:18:46 PM »
Hello everyone. I am new to this forum. I am a member of sohc4.net
Seeing as my bike is European I was hoping you could tell me your experiences with the 649A carburetors on the cb500. I understand England receive 627B carburetors but being so close to Germany etc. I would guess there was more crossover of bikes than here in Canada and the USA.
I wanted to know how the bike ran in stock compared to without the air duct assembly and if any of you used 100 main jets in 649a carburetors instead of the stock 78's.
Lastly what settings were used on the carburetor and bike for these various setups to run nicely. (Main jet, slow jet, air screw turns, needle clip position from top, float height, air filter type(foam or paper), exhaust type(Original or aftermarket), spark plug)
Pages: [1]
|
Show Posts