Cb600 rebuild starting issues

slim01

slim01

slim01

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1 Sep 2010
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Bristol, South West
Hey guys, having a nightmare with a new restoration on a 2000 Honda hornet cb600.

Had about 6 weekends spent on it (mostly painting) fired it up last week, fine. Fired it up today, started instantly (always needs choke from cold).
Got it up to temperature, took for 3 min slow test run. Fine. Was running MUCH better than before restoration (smoother idle and throttle response).

Took it for another run - stalled it (after getting stuck in some mud), and when it fired back up throttle response felt weird and bike sounded odd, maybe like one cylinder not firing - sounded and felt like maybe is blocked or restricted in some way, don't know how to describe as not a pro.
Rode it back and had to keep 20% throttle or it'd cut out. Just about starts now but as soon as I take throttle off it dies. It is work to get it to start even though.


Things we've done...
-New spark plugs
-New oil
-New clutch
-New motobatt battery
-Carbs cleaned
-Air filters (aftermarket trumpet ones moved to different positions as ones on outside scratched).
-Cleaned both ends of clutch, choke and brake cables
+other things like Painted everything including tank, (but checked all hoses etc are back), did rear light unit/tail tidy, new front calipers

The bike has about 20 miles of reserve petrol in it, but this was treated with redex about 2 months ago (same fuel). Not sure if that's an issue.
Gonna see if we can start with the tank off as got one of those drip things.
When we took the tank off my mate noted the petrol was very dark - quite odd?

Any ideas what it could be guys? Odd it was running OK then just started acting badly.
Based on my description - Am I likely dealing with misfiring? And what is good place/guide to start?

Already spent FAR too many weekends with my mate on this bike I feel bad for him.

THANKS FOR ANY HELP IN ADVANCE!
 
First thing first is fresh fuel, drain the carbs and tank of the old stuff first.
It may have sucked some crud through so the carbs might need a proper clean.
 
tom_e said:
First thing first is fresh fuel, drain the carbs and tank of the old stuff first.
It may have sucked some crud through so the carbs might need a proper clean.
Click to expand...

Was thinking this, however we had the bike running for a good 15 mins to get up to temp before taking for the test ride. Rev'd a few times, not much, but was sweet as a nut. Another 5 mins of riding the bike up n down - perfect. I guess yeah could still have taken some crud in at some point...

There's been fresh fuel put in there now however. Also tried using one of those bottles with the tank off, nothing.

Few mechanic type friends have both suggested because it started and was running fine it's likely to be an electrical issue - bad reg/rec (a known issue on these bikes) or cdi unit.

Gonna add your suggestion to the "to try" list... Anything else you'd suspect? Not sure if you agree with the electrical issues being likely... Guess I have to try everything anyway
 
Honda's do love to cook their electrics might be worth a quick multimeter check as again it's easy enough but like you I think it's unlikely, unless a coil has died possibly.
Have you checked you're getting a spark on all plugs?
 
Yeah quite a few peeps are suggesting the same as you guys - we really need to check the spark to those plugs. And coils.
It's a damn pain on the hornet though cos the frame goes right down the middle covering access to 2 of the heads/carbs down the middle etc. This is why my mate skipped balancing them with his dial things, couldn't get to two of the nipples he needed.

Tom e you had a few honda's that cook electrics then? It's really odd and my mind keeps on going back to the fact we've had numerous strange electrical issues so far...
1) when picked up the bike it wouldn't start off old battery, bumped ok, recharged dead battery by riding 20 mins, started ok. Turned off and on around 6 times expecting problem to have gone, 7th time, nothing.
Portable battery unit made it start instantly 7/7 times instantly, as did jump leads from a car (maybe a bad idea... But not as bad as the idea that this was all just because of a screwed battery and bought the bike anyway! LAST TIME EVER I DO THIS!).

2) a previously working front headlight smoked and burned up last month. Reason unknown. New bulb ok.

3) rear tail light, previously working, was simply cut off then put on few weeks later after painting - dead as a dodo. Wouldn't light off a battery. Nothing.

And now this no starting issue again. I'm confident if I had a 100% charged battery it would fire up again. However, I never had that weird misfiring/starved throttle response or odd noise feeling before which makes me feel its something new.
 
If you're burning bulbs, it could very well be the RR has failed, and is over volting. Before you boil another battery, and / more, check the R/R.
 
Munchies said:
If you're burning bulbs, it could very well be the RR has failed, and is over volting. Before you boil another battery, and / more, check the R/R.
Click to expand...
Yeah two bulbs so far. One front one rear. We have had the front cowl off to paint mind, and rear one was snipped, then did some work on the rear cabling and ended up putting like bullet connectors on and changed rivets to push clips on the protective panel which goes over rear underside of seat unit.
This panel that covers the cables was hanging off when I got stuck in the wet mud, and loads got flung up the bike because didn't have hugger on. Not sure if it's coincidence that's exactly when I started to have the issues, but couldn't see any mud or moisture on the connections and was only rear lights and indicators anyway.

You rekkon it could be linked to reg/rec yeah? OK will do. Guess I need to check for any burning or bad contacts, maybe even bad solder inside the unit. I always thought the reg/rec was more for just battery charging issues see. I know battery is charging.

I've heard they are common to go on three bikes but can't find the symptoms listed anywhere really.

Yeah battery on there is a new £50 motobatt so would like that not to fry .
I've got one of those pricey ctek to go chargers I haven't used yet, I think it's supposed to tell you if battery is damaged. I expect its well below half now - started to sound low last time tried to start.

Thanks guys
 
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Munchies said:
If you're burning bulbs, it could very well be the RR has failed, and is over volting. Before you boil another battery, and / more, check the R/R.
Click to expand...
Actually do you know where I can find the readings I should be getting?
I think battery was at about 1.3v last time we checked (bike on).
I know it should increase when you rev it but what kind of numbers should I be looking at? It's not bike dependant for charging no? All bikes should eg do over 1.4v to charge?
 
Munchies said:
You should see around 14 - 14.5 volts, typically around 4 - 5k RPM across the battery when it's charging.

Then use your multimeter to check the R/R. Probably easier to just link a video: https://www.youtube.com/watch?v=-2jWIkhy1fo
Click to expand...

Legend thanks.

Just an update for everyone.

Cleaned all the carb jets (was like 3 per carb - 1 main and one idle) ans also the bowls.

After this the bike started up pretty much right away with a bit of carb cleaner as easy start.
After that was starting fine but idle was quite high and revs were crazy high, after revving they wouldn't die down and just stayed at say 5k for example and even started to increase all by themselves.
We adjusted the idle valve down, and bike was idling low (about 1-1.1k) but seemed to be happy there.

Was starting fine. Started once on Wednesday (3 days after we thought we fixed it) and today (Saturday) nothing. Absolutely no chugs from engine. Starter motor goes but engine not even close to starting.

Also, not sure if related, but two odd things to note:
1) we used a random h4 bulb from workshop as last one died (read above) and noticed before leaving last sat the light was very hot.
Riding On motorway (about 15 mins later), main beam stopped working, high beam worked for 2 mins then blew up.
I do have some new h4 osram night breakers to try.
2) after trying to start today, for a good 3-4 mins of total cranking time, plugged battery into my new ctek charger and it said only 1 hour to go out of 8... So like 90%+ battery left? That seems odd to me. Would have thought would be almost dead, no?

I guess next point of call is reg rec as you guys are saying.
My other mate rekkons brand new carb. However the bikes been running so would you guys rule carbs out as an issue?
 
Oh and also we checked the sparks last weekend and yeah the one on the left and right (only ones with easy access) both were sparking.


After it did start, the symptoms of the misfiring (the weird sounding and kind of starved/restricted throttle response) had gone. Sounded sweet right away, and after sorting the idle switch was idling nice.
 
Clean fuel filter and check fuel pump (if it has one) is working. Sounds really similar to what was happening with my 400 Bros. Mainly due to a rusty flakes from the tank getting in the fuel then blocking the filter.
 
UPDATE:
Ok gave up trying to start, so my mate came down to bump, I said ok this is what it's doing... ANNNNNND it starts first damn time. Literally wtf??!?!?!?!?!?!?!?!?!?!!?!?!?!?!?!?!?!?

Took it out for a 20min burn, and apart from one occasion where I felt some sort of restricted power loss moment (was opening throttle up but didn't wanna go past 80mph) which then cleared itself, it didn't miss a beat.
Went to start it... Nothing.
Tried again, this time starting the starter immediately after turning the key. Fired up. Idled/rode perfect.

*note* There is no fuel pump. Fuel is fed via vacuum/hose.

*note* New lightbulb worked for +30mins no issue.


bloodiedathame said:
Clean fuel filter and check fuel pump (if it has one) is working. Sounds really similar to what was happening with my 400 Bros. Mainly due to a rusty flakes from the tank getting in the fuel then blocking the filter.
Click to expand...

ahhhh yeah this is a real good shout, it's odd that these issues come and go as they do, making me think it's not rec/rec, but this might explain. Thanks.
 
bloodiedathame said:
Clean fuel filter and check fuel pump (if it has one) is working. Sounds really similar to what was happening with my 400 Bros. Mainly due to a rusty flakes from the tank getting in the fuel then blocking the filter.
Click to expand...
So did you have to get tank cleaned in the end professionally? Did you keep getting issues?

When I painted mine, I did notice it had a lot of rust around the bottom edge/lip, both sides, but inside the tank looks fine on the bit I can actually see.
 
I used a chemical in the tank that basically bound to the rust and coated the whole of the inside of the tank. I can't remember what it was called as this was nearly 15 years ago! I seem to remember it being a bit like liquid fibreglass. If I can find the brand I'll let you know but it definitely fixed the problem.
 
Could be an air leak? Would explain the intermittent odd idle, and perhaps the in-tank pre-filter is not flowing nicely, causing float level issues under higher loads?

When I had a fuel pump issue on the CBR400, it did some odd things like that. Also, never underestimate what a low fuel, or dodgy fuel will do to keep a bike engine from running nicely!
 
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Malt_Vinegar said:
Could be an air leak? Would explain the intermittent odd idle, and perhaps the in-tank pre-filter is not flowing nicely, causing float level issues under higher loads?

When I had a fuel pump issue on the CBR400, it did some odd things like that. Also, never underestimate what a low fuel, or dodgy fuel will do to keep a bike engine from running nicely!
Click to expand...

Well... Took it out for a damn good run yesterday (2+hrs). Full tank of fresh petrol:
-Took me 5 mins to start it.
-then, Bike was amazing, didn't miss a beat! Very quick. Nice idle, great sound. Was starting/stopping fine (about 7 times).

RAC brought it back in the end anyway, but was unrelated issue: coolant tube cracked as was put on so tight by last guy. Was squirting out everywhere at high temp pressure. Damn.
-back at house, wouldn't start again (maybe 20-30 short cranks and eventually it did, even without any choke and must have been cold - I was experimenting : wasn't expecting it to start with no choke).
Did hear a weird air noise a few times here but couldn't pin point from where. Assumed was normal or from being wet.

So how the hell do I test for air leak? You mean from like a gasket in the engine or something? Wouldn't something like that prevent the bike from running perfectly for 2+ hrs?

It literally is just starting issues now... And literally the moment the bike ignites petrol, it fires up. There's no "almost starting", it's all or nothing (by nothing I mean it just cranks and cranks).
 
Update...

Bump starts instantly.

Is pretty much fine except when cold starting.

Not sure if that means anything to anyone.
 
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