Idle low rpm and engine cut off problem

[Austins]

Well, this a long story started a couple of weeks ago, so read with patience...

I bought all 24k km service parts online and changed by a local mechanic about 2 weeks ago.

Also at the same time tried a new fuel from Shell for the first time (V-Power something blah blah..., a lot more expensive here in Thailand, but I read it has some cleaning detergent so not bad to do a couple of full tanks sometime to clean !).

So first full tank of that fuel was a few days before service , then another full tank a few days after. So no problem I noticed until the day I put 2nd full tank and that was like 3 days after the service.

Bike idled at low rpm (1350 , before never came down from 1500 line, ever) that was when warn, also cut off sometime. No problem starting cold, I think fuel injector compensates for cold and burn richer, so only problem when warm.

I didn't think of it much, as it did not effect running at speed and in fact fine at traffic lights etc...

Even I went on 1250km round trip last week, and put 3 or 4 full tanks of my normal gas in. But problem with idle remained.

Took to the mechanic yesterday and got the spark plug out, I was concerned maybe a NGK copy from internet shop, checked gap and resistance with Ohm meter, compared with old one that came out, all good, I researched the web a bit, this plug is good, since then 3 other mechanics also looked at it, also tested with another used different type of plug they had, same idle issue.. !

Checked battery, although old, no problem, perfect voltage. Checked air filter, just changed to new at service, so no problem. I also used different oil this time, 10w30 Honda ProTech fully synthetic MB, before used Shell 5w40 100% synthetic Ultra Scooter MB, but I don't think that and oil filter or the new belt causing idle issue ...!? or do...?

Today the symptoms are far worse, idle cut off and bad warm start all the time, take off and acceleration stutter and cut off at traffic light every time, terrible now....!!! Just now came back from Honda dealer shop, they put it on the computer and checked everything, also checked spark plug and air filter again, nothing showing wrong at all, they are baffled..., mainly think of bad fuel, he says bring the bike for a couple of days so we rip open the hell out of the engine... , with no clue what is wrong that means "Big Cost" ...!!!

My friend said put some fuel injector/system cleaner additive, I might try that..., but couldn't find any locally.

It's the worst thing when everything seems to work fine, but there is a problem...!

Add to that Honda guy noticed left back shock is leaking oil, I said change seal, said no way, it's not like the front, back can not be repaired, need to replace new and also both sides..., another "Big Cost"... ...!?

Anyone says "Honda bullet proof blah blah..." again, I laugh in their face... -:)

[easyrider]

Probably bad fuel( water).

[gn2]

Fancy fuel is a waste of money.
Buy the same stuff everyone else uses, it sells faster so it won't be lying around in the storage tank picking up moisture.
Drain and refill with fresh fuel.
Don't use any additives, they're already in the fuel when you buy it.

[Austins]

Yes, someone else also said drain the fuel, but I counted I have done over 1200+km or so since that expensive fancy fuel - about 4 or 5 tank of fuel emptied and then refilled (I usually wait for tank to empty quite a bit and fill up about 9.5 liters at every visit to gas station). So if anything this should get better but no, it's getting worse....

So it must have damaged something permanently, and pretty badly if it was that fuel...!

I'm still suspecting the spark plug or air filter, but what can go so wrong with them - something makes me think is since two days ago when I came back from the trip and they opened the spark plug and air filter to check it got worse ever since, have they damaged any threads, tightened plug too much ... or damaged cables, screws etc. ....!? So every time they open it gets worse...!!!!!

Going to another Honda dealer today in another location, see if they have any bright ideas...

[gn2]

Stalling at low rpm is usually related to fuelling or ecu issues.
You need to get it to a proper main Honda dealer with the required diagnostic equipment and trained technicians for them to take a look at it.

[Austins]

So I waited a few days before posting, in case what occured was a temporary thing...!

It's a mystery really, before I take the bike to another Honda dealer, I thought I check things myself one more time. I don't have space or tools, so went to the small local repair shop who have been friendly and patient with me and ask for their tools and opened air filter and spark plug myself.

Took air filter completely out and started the bike, I asked the last Honda dealer to test this in case the filter is blocked, he said no can do...!!! Anyway, bike idled with same problem, so put back and closed that up.

On to old spark plug before service, check and adjusted the gap, put in but bike would not even start at all, zip...., made the gap a bit bigger or smaller and tried again, no start...! Engine cranked long with battery and starter motor but never turned even once on its own...

Then tried the new spark plug put on two weeks ago, adjusted gap again, 0.85mm (recommend is 0.8-0.9mm), and now the bike would not even start with new plug ..!!!??? Tried re-adjusting the gap and tried many times, no start... I even let the plug out on metal and cranked the engine , could visibly see the sparks happening. Checked on Ohm meter for both, seemed fine...

What the hell...? The bike not starting I couldn't take it to Honda or anywhere. They have a small parts shop there and he had my plug, NGK and exactly the same one as the other two I had. So I said what the hell let's a get a new one. The kid came himself to put it in but I made sure he does not tightened it too much and we did not touch the plug like testing it on Ohm meter or change gap etc. , just straight in.

Oh boy, behold, the bike started on first push of the button and idled perfectly....!? No more erratic idle whatsoever, still at 1400rpm, but no issue for 3 or 4 days now, warm or cold...!!!

No idea what is wrong with the other two plugs, I have many theories, but not sure, maybe bad fuel damaged them, or adjusting the gap, or these kids and myself damaged them opening and closing, it's a bad angle and need correct socket and rachet extension etc. (I recall the sparks I saw were yellow, I think they are supposed to be blue, so maybe weak and have a leak short in porcelain etc. ...!), I just can't be sure but it's working perfectly now, saved from a lot of hassle and cost...!

Also found a shop that replaced many back shocks on these bikes with YSS (this is the first thing Forza buyers do here, like a fashion statement...!) , so he had many OEM original shocks, he put on two fairly new looking used shocks for me very cheaply, so all is okay for now...

[Old Scoot]

Or maybe there was/is carbon buildup between the middle electrode and the ground of the spark plug, I always clean that space when I have to check the plug if the gap is still in spec

[Old Scoot]

Somewhere, someone wrote this:
I always use NGK Iridium plugs. Last a long time, and change them every year
https://ngksparkplugs.com/en/products/i ... park-plugs


every year? do you ride 60000+ km every year? because that's how long they last, changing them earlier is just throwing money away

[Austins]

Good point about carbon built up, I should have cleaned them more...., I remember many many years ago we used a very fine sandpaper for cleaning, adjust the gap, and reuse plugs in cars for years, now they become a throw away item...!

After this episode with plugs and having to buy two, I might consider iridium next time, but I won't touch this plug for another 24k km, very fussy piece of work - on my Forza anyway ... (probably if opened and put back , it won't start again like the other two...!!!).