my 450 has a weak start, then dies after short idle ...

701 Views 14 Replies 5 Participants Last post by gowest, 8 mo ago

gowest

Discussion Starter · 9 mo ago

Hey there --

Would love some advice. So for the past three weeks, my Rebel '86 450 has been feeling "weak," especially as I downshift towards a light/stop sign -- to the point where I've been throttling it to give it some life.

Then yesterday, after a week of no-riding, I couldn't even keep the engine alive upon start-up! Per usual, I'd turn on the choke, kick on the engine, turn off the choke after 5-10 seconds, but while this routine has always worked perfectly fine for the past two years, this time the engine simply died. And I've done this about ten times since, and it's been the same result.

-- There's enough fuel in the tank (it's low, but there's enough);
-- My 18-month old battery drained about two months ago after I accidentally pulled the key out leaving the bike in the ON position -- BUT I trickle re-charged the battery, and it seemed to work fine afterwards -- until yesterday.
-- When this first happened yesterday, I thought it was a power/electrical issue, so I again trickle re-charged the battery to full, and this morning -- same thing! -- the engine has a weak start, then stays on for about ten seconds, then dies.

What's the issue?

-- Would a brand-new battery fix it?
-- I'm not a mechanic, don't have a garage, so unless it's something pretty easy for me to fix, I'm not sure what I'll need to do.
-- This bike has been in such a great condition, with no issues, so this is really baffling to me.
-- I had been hoping to keep this bike for another year, then upgrade to a bigger and newer biker, but now I may wanna do this sooner, but I still gotta fix this to resell.

Thanks!

1 - 15 of 15 Posts

SoakedKarma

· #2 · 9 mo ago

While a battery may not be the best once started it has no influence on ignition/spark.
exciter coils attached to stator supplies >100vAC to CDI which eventually snaps off spark plug end..
Ignition system is completely separate from battery, while hard on volt regulator/rectifier engine will run without battery once flywheel rotated fast enough..

Is there a change in how long engine runs if enricher/choke cracked open a little or even more than a little?

gowest

Discussion Starter · #3 · 9 mo ago

Thank you for helping.

The bike I got used 18 months a, in very good condition, came with this, so it’s not stock:

-new authentic Mikuni carbs tuned by 951 custom -new Uni oversized intakes

so it has a choke on two sides, I usually choke both sides, but I kill the first one almost immediately, and kill the second choke usually about five seconds in, which has never been a problem.

After I kill the second choke, since yesterday I’ve had to throttle to keep the engine alive, and that seems to keep the engine going a little longer, but it still ultimately dies after about 10 seconds. Again, this hasn’t happened until the recent loss of power I’ve noticed two weeks ago, and the inability to stay on after start up yesterday.

Emil

· #4 · 9 mo ago

gowest said:
.....
-- I had been hoping to keep this bike for another year, then upgrade to a bigger and newer biker, but now I may wanna do this sooner, but I still gotta fix this to resell.

Thanks!

Yesterday I was at Harbor Freight & there was a guy working on his HD in the lot. When he saw the 86 250, he immediately said that he's been searching for a Rebel 450.
If members here don't snap it up, there are many others that still know their value!

Reactions: 1

SoakedKarma

· #5 · 9 mo ago

Check your fuel supply,, pull hoses off apply vacuum to petcock valve to allow free flow of at least a pint, quart into container would be a better test with a low tank to see if flow slows or stops..

gowest

Discussion Starter · #6 · 9 mo ago

You might be right, even though I could hear fuel in the tank, I’ve always noticed in the past the bike starts up very differently with a full tank, so there might be a clog. I’ll check.

flitecontrol

· #7 · 9 mo ago

Don't know if it's applicable to your 450, but all my 250s that needed choke to start would die if I took them off choke as quickly as you do. Usually able to slide it off completely after a couple of miles of riding.

gowest

Discussion Starter · #8 · 9 mo ago

flitecontrol said:
Don't know if it's applicable to your 450, but all my 250s that needed choke to start would die if I took them off choke as quickly as you do. Usually able to slide it off completely after a couple of miles of riding.

With this bike, for some reason, the bike will die if I keep both chokes on, and if I leave the last choke on for too long it will also eventually die. Is that weird? And this is why I release them pretty quick after start up, which hasn’t been an issue, but I am also in Los Angeles weather.

Emil

· #9 · 9 mo ago

Location, Location, Location! It makes a huge difference, Yes. In NE Ohio you'd probably need the choke most mornings, at least after September.
The aftermarket carbs are harder to figure though. I think that SoakedKarma has you going in the right direction.

gowest

Discussion Starter · #10 · 9 mo ago

SoakedKarma said:
Check your fuel supply,, pull hoses off apply vacuum to petcock valve to allow free flow of at least a pint, quart into container would be a better test with a low tank to see if flow slows or stops..

Hey, would Sea Foam help? Worth a try?

flitecontrol

· #11 · 9 mo ago

Is there an inline fuel filter between the tank and carbs? Wondering if some crud got in them.

SoakedKarma

· #12 · 9 mo ago

Seafoam's MSDS listed ingredients
40-60% Pale Oil (CAS 64742-54-7),
25-35% Naphtha,
10-20% Isopropyl Alcohol "IPA".

Pale oil, a light machine oil sometimes used in electric grid transformers for cooling.. a lubricant

Naphtha aka white gas or Coleman lantern fuel, a solvent.

Isopropyl alcohol, a good gas dryer..

There is no additive that will replace actual inspection and some flow testing..
You can unscrew bottom of petcock strainer cup #9 look for rust.. There is also a screen inside tank #5..

See less See more

Reactions: 1

gowest

Discussion Starter · #13 · 9 mo ago

flitecontrol said:
Is there an inline fuel filter between the tank and carbs? Wondering if some crud got in them.

Not sure at all, but I will take a look and see, just afraid of opening up a can of worms I can’t put back.

garicao

· #14 · 8 mo ago

gowest said:
Hey there --

Would love some advice. So for the past three weeks, my Rebel '86 450 has been feeling "weak," especially as I downshift towards a light/stop sign -- to the point where I've been throttling it to give it some life.

Then yesterday, after a week of no-riding, I couldn't even keep the engine alive upon start-up! Per usual, I'd turn on the choke, kick on the engine, turn off the choke after 5-10 seconds, but while this routine has always worked perfectly fine for the past two years, this time the engine simply died. And I've done this about ten times since, and it's been the same result.

-- There's enough fuel in the tank (it's low, but there's enough);
-- My 18-month old battery drained about two months ago after I accidentally pulled the key out leaving the bike in the ON position -- BUT I trickle re-charged the battery, and it seemed to work fine afterwards -- until yesterday.
-- When this first happened yesterday, I thought it was a power/electrical issue, so I again trickle re-charged the battery to full, and this morning -- same thing! -- the engine has a weak start, then stays on for about ten seconds, then dies.

What's the issue?

-- Would a brand-new battery fix it?
-- I'm not a mechanic, don't have a garage, so unless it's something pretty easy for me to fix, I'm not sure what I'll need to do.
-- This bike has been in such a great condition, with no issues, so this is really baffling to me.
-- I had been hoping to keep this bike for another year, then upgrade to a bigger and newer biker, but now I may wanna do this sooner, but I still gotta fix this to resell.

Thanks!

You might check the exhaust pipes (carefully) to feel if they're around the same temperature. Or remove the spark plugs after blowing out any crud from the hole area. Check to see if the plugs look the same---one may be fouled.

Reactions: 1

gowest

Discussion Starter · #15 · 8 mo ago

UPDATE, UDPATE:

Hey, y'all -- just wanna share what's been happening, maybe I'll get some feedback as to my progress, 'cause this issue ain't resolved yet:

(HISTORY: Suddenly, a few weeks ago, w/o any precipitating event I can think of, my 450 Rebel would have a weak start, then easily die after a few seconds -- and it certainly couldn't stay alive unless I applied throttle, and even then it sometimes died.)

(And just FYI, some of these latter steps were walked-through with me via FaceTime by the nice fella who sold me this bike.)

1) I put in a new gallon of fuel to make sure I'm not on empty, tried again, no bueno;
2) I added about a half-can of SeaFoam, let it sit for a few days, tried again, no bueno;
3) I bought a brand-new Yuasa conventional battery, tried again, no bueno -- so I guess it ain't a battery/voltage issue;
4) I removed both air filters completely off (aftermarket Mikuni carbs), tried again, no bueno -- so the nice fella doesn't think it's an airflow issue;
5) I tweaked the idle bolt, loosening and tightening, tried again, no bueno -- so I guess it's not the idle adjustment;
6) I removed both spark plugs, touched the plug threads against metal, started bike, I noticed tiny sparks, so the nice fella doesn't think it's bad spark plugs;
7) I put the spark plugs back in;
8) As of now -- today, I've removed the Mikuni carbs from the bike, and the nice fella said if I can bring it to him (an hour away), he can help me inspect the idle/pilot jets to see if they're clogged, and have them cleaned for me, and then we can reinstall carbs and go from there. I hope to do this tomorrow/following day, will know more by end of week, hopefully.

Any thoughts about any of this?
Are we headed in the right direction?

This bike has about 13,000 original miles on it (I've put in about 5,000 of it, have done two oil changes), and it doesn't get ridden a lot or any abuse from me. It sits beneath a cover, occasionally gets dusty when it's windy out, but nothing crazy, I don't think.

I hope it's an easy fix.
Anyway, will report more, but the nice fella said based on the symptoms, he wanted to isolate between Air, Electrical, Fuel ... so that's the plan.
Right now, he thinks it's the idle jet.
BUT he also thought it was a low-voltage battery issue (since I did accidentally drain my battery few months ago).

Ugh.
I miss being on my 450. With my smile against the wind.

Thank you!

See less See more

1 - 15 of 15 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.