Author Topic: ignition or other faults (Read 1789 times)

my79650 · « **on:** April 20, 2014, 08:54:52 AM »

Stock 79b650 engine. Been doing this over a year at anything over 50mph. The PD50 carburetors are clean; bench synched; swapped rh coil as if had a big crack the length of it(2 1/2 inch). Idles good at 1200rpm. Anyhow on the road when you give it some to keep the speed even going up a small hill it will hesitate, do the same on the flat when you want to speed up a little. This also happens with my 75 750 carb rack installed. Today after the coil swap of course it sounded fine in the yard. Same hesitation on the road at 50/60 mph.
After a few miles i went full throttle, slight hesitation as made it up 7000 rpm then it would kick in, then out, did this for bout a mile then i had to let off as the hiway ramp came up.
Did a spark unit test; (disconnect and reconnect); both work. Tested the ohms on both coils (3.0 lh/3.2rh); also tested the pulsers:480/512; these were cold measurements i took the other day.
I know new plugs would help and trimming the plug wires to new ends ; do that this week. Adjust valves and timing chain too. It is getting gas; i'm trying not to pull the carburetors again as its a pain in the a$$ to hook my air box rubbers back on as they are getting a bit rough. Floats are good as are needles, when i did the cleaning they weren't overflowing so i just cleaned everything up and put the carb rack back together. Any thoughts r suggestions appreciated.

KayOne · « **Reply #1 on:** April 20, 2014, 09:32:05 AM »

Had similar symptoms on my '79 750 DOHC, they run the same transistorized ignition. Turns out one igniter was bad. The igniter take the signal from the pulsers and switches (fires) the coils.

http://www.procomeng.com/estore/featured-products/pe-c-mh900-a.html

my79650 · « **Reply #2 on:** April 20, 2014, 04:57:30 PM »

That's what i think it is also. I used my last spare last summer, but 30+yr old electrics can't last forever. Thanks for the link. Same price as Electrosport for them. Since i never lost my online order virginity its time to figure this out. Or do the Pinhead upgrade.

my79650 · « **Reply #3 on:** April 21, 2014, 03:27:25 PM »

I ordered the new ones from Electrosport; them and Procom had the same price; probably be a few weeks getting up here to New Brunswick Canada; but i got other things to do til then.

my79650 · « **Reply #4 on:** May 04, 2014, 11:54:07 PM »

New units cleared Customs on May 1. Should be here by end of this week.

KayOne · « **Reply #5 on:** May 05, 2014, 03:06:15 PM »

Hopefully this will cure the problem in time for this seasons riding.

my79650 · « **Reply #6 on:** May 06, 2014, 05:09:45 PM »

Got them today, installed, performed better up to 65 mph. Went WOT and it acted up again. Going to swap fuel filter and check vent lines and plugs before i do anything else as it started acting like it wasn't getting fuel.

my79650 · « **Reply #7 on:** May 11, 2014, 12:10:40 AM »

Changed gas filter and replaced spark plugs. Checked valve clearance and replaced the leaking head bolt pucks while i was there. Anyhow i am driving it to work tonight. Hoping i don't need to pull carburetors and redo them. All ignition parts are working good so if there's any more problems then it will be in there.

Deltarider · « **Reply #8 on:** May 11, 2014, 01:19:15 AM »

Quote

I know new plugs would help and trimming the plug wires to new ends ; do that this week.

That's where I had started.

my79650 · « **Reply #9 on:** May 18, 2014, 07:38:59 AM »

Did all the normal checks; trimmed plug wires; new ngk d8ea plugs; adjusted cam chain, valves adjusted to spec. Pulsers tested ok(electric or electronic points replacement stock part), went and pulled the carburetors again. I bought these stock pd50's from a salvage yard, they were complete and i gave them a major cleaning and swapped over my good jets and needles, floats and all my good parts over from my other set. After a year i had to clear out the tubes as a few had clogged holes. Checked the float levels and had to adjust them. Will know what it does when i get it out on the road.

my79650 · « **Reply #10 on:** May 18, 2014, 10:30:04 PM »

The accelerator pump is new, installed last June. No working choke at all, flaps and screws are sitting in a tobacco can in my shed, twist the throttle 6 or 7 times and it starts right up and stays running after a few minutes of babysitting. I don't have the time or patience to build a meter. Not going to pay the local bike shop $60 for a 10 minute job, but when i get a chance i will check the local rental shop for tools they may have one i could rent. The restriction ports? You mean where that little brass bearing is on the carb body? They're fine, i get good spray.
Twotired did i say bench sync eliminates vacuum? I did not, it gets me running, as long as your adjusters are fine, not beat up or stripped a bench sync using a small drill bit will get you running to diagnose everything.
I was getting 40mpg out of this rack, not bad for something getting that #$%*ty ethanol gas. You can't avoid it up here as the pump lines hold at least 3 quarts of ethanol before i get the supreme as in my tank.
To adjust the acc. pump is to bend the tab, that was never touched by me as it was working fine, drive Monday to see what happens.
This did the same thing with the 750 carbs that are in my signature photo.

trueblue · « **Reply #11 on:** May 18, 2014, 10:45:16 PM »

If you haven't done it already, set your reluctor air gaps. They do change even though nothing actually touches. Also make sure your advance mechanism moves freely, if it doesn't pull it apart, clean and grease it. The reluctor clearance should be between 0.012" and 0.016". If it is outside these measurements it causes surging and a general lack of power.

my79650 · « **Reply #12 on:** May 19, 2014, 06:37:12 AM »

That's the one thing i didn't think of even tho it tested fine on my multimeter. Check that next. when i check this i have the pointer lined up with the magnetic strip on the reluctor correct the measure right?

trueblue · « **Reply #13 on:** May 20, 2014, 01:55:30 AM »

That's right, at the same place you do your static timing. I always set mine to 0.012", it makes a huge difference to how they run.

my79650 · « **Reply #14 on:** May 20, 2014, 07:21:38 AM »

thanks man; other things happening this week; be friday my day off before i can get back at it.

trueblue · « **Reply #15 on:** May 21, 2014, 02:01:51 AM »

No worries mate, let us know how you get on

my79650 · « **Reply #16 on:** May 23, 2014, 12:05:09 AM »

I checked before i went to work, 0.012 and 0.013, matched the right one to the left. Removed the advancer, cleaned and oiled. I set timing to the firing mark for 1 & 4. Got to remove it again as i'm off, won't start now. My fault for hurrying. Got the manual so i will reset it Friday.

trueblue · « **Reply #17 on:** May 23, 2014, 12:44:26 AM »

Just make sure you didn't reassemble the advance unit back to front. If I remeber correctly there is a dot on the base that the reluctor point lines up with

.

dave500 · « **Reply #18 on:** May 23, 2014, 01:10:13 AM »

the same applies with the points systems!the cam lobes for the points will be 180 out if the advance unit is reassembled incorrectly.

they can be reassembled the wrong way if you don't look close!akin to getting your distributor 180 out?

my79650 · « **Reply #19 on:** May 23, 2014, 06:31:40 AM »

Thanks; i remember greasing and turning it round to make sure i had everything cleaned and oiled; forgot bout the mark.

my79650 · « **Reply #20 on:** May 23, 2014, 10:10:23 AM »

When i removed the advancer the little pin to line it up with the crankshaft was in the pilot hole on there. I fished it out with a small magnet. I used some aviation sealer on the pin when i put it back on the advancer unit. Letting it set a few hours before i put it back on the crankshaft.

my79650 · « **Reply #21 on:** May 23, 2014, 04:32:57 PM »

She runs, the pin stayed in place. Go for a drive to see if there's any more issues

trueblue · « **Reply #22 on:** May 23, 2014, 10:33:14 PM »

That's the other one that can stuff you up. I had forgotten about that, I had the exact same issue with mine. Hopefully it settles down for you.

my79650 · « **Reply #23 on:** May 24, 2014, 06:42:13 PM »

Worked like a top today, 50 mile drive to my father's and back. She kept wanting to go. Stopped cranking the gas at 90 mph, lots of cops out today. Hasn't performed this good since i bought it four years ago.

KayOne · « **Reply #24 on:** May 24, 2014, 07:17:20 PM »

Congrats, you hung in there and won....enjoy your bike!

trueblue · « **Reply #25 on:** May 25, 2014, 02:08:30 AM »

That's good to hear, I took my 650 for a run today, it had been sitting for nearly 6 months and went like a champ. Not much goes wrong with these bikes, but they do like having everything just so. I find with mine that even a slight bit out of tune and it makes a huge difference to how it runs.

my79650 · « **Reply #26 on:** May 25, 2014, 06:04:31 AM »

Just rolled over 61,000 kms on the meter yesterday; i plan to keep it til there's nothing left. You're right as long as its taken care of it will last forever. Let's see; up here where i'm at in Canada i can get to the first week of November til its too cold to drive. Then most times i can get it out round the middle of March. Average 5 months for winter storage.

trueblue · « **Reply #27 on:** May 26, 2014, 01:58:44 AM »

Mine has about 85,000km on the clock. Around here we can ride all year, though summer can be a tad uncomfortable in the heat. The reason mine has been sat for so long is more lack of time on my part than the weather.

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Author Topic: ignition or other faults (Read 1789 times)