innova backfire

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1chris1
Posts: 15
Joined: Thu Sep 07, 2017 9:04 pm
Rides:: BMW R 1150 GS HONDA innova 2008 honda nss 300 forza

innova backfire

Post by 1chris1 » Wed Oct 10, 2018 9:30 pm

had my innova carb cleaned because it had stood for 18 months or more, bike starts and runs fine, no choke required.
only problem i have is that when decelerating i get a loud popping noise/ backfire.
i have checked the spark plug and it was very dark, almost black but not oily. the plug is a ngk cpr6ea-9.
i put a new plug in but still have the same problem. the air filter was changed about 6 months ago.
i have read that my fuel air mixture is probably too rich. is this an easy thing to cure or do i need to take it to a mechanic.
i can do basic maintenance like oil changes,air filter change, brake pads etc, but never had anything to do with carburettors.
don't want to make things worse.
any advice appreciated.

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lucky
Posts: 988
Joined: Thu May 17, 2012 5:41 pm
Rides:: (2001) X Reg Honda Cub 90 MT (Stolen) 2007 Honda Innova ANF 125
Location: Bolton, Lancashire England

Re: innova backfire

Post by lucky » Wed Oct 10, 2018 10:07 pm

I have the same problem with my '07 carb Innova, hopefully someone has a fix for this :) .

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onittino3
Posts: 952
Joined: Fri Sep 04, 2015 6:52 pm
Rides:: Honda C90, Honda Cb500x
Location: Merstham Surrey

Re: innova backfire

Post by onittino3 » Wed Oct 10, 2018 10:36 pm

The Innova has a PAIR valve, which could be the cause as it adds Air to the combustion on deceleration for emissions, in the Haynes Manual it explains how to test it, i would start looking for air leaks around the chrome pipe were it enters the head as these pipes do rot and the gasket can fail.

Diddly
Posts: 201
Joined: Sat Sep 19, 2009 6:51 pm
Rides:: Honda ANF125 Innova;
Location: North East

Re: innova backfire

Post by Diddly » Thu Oct 11, 2018 8:08 am

Check the exhaust sealing washer that seals between the exhaust pipe and cylinder head.
It's cheap to buy. Old one may need prising out of head with a screwdriver or picking tool if flattened.
Careful with exhaust head nuts, 12mm spanner if Honda or 13mm if replacement.

Diddly

1chris1
Posts: 15
Joined: Thu Sep 07, 2017 9:04 pm
Rides:: BMW R 1150 GS HONDA innova 2008 honda nss 300 forza

Re: innova backfire

Post by 1chris1 » Fri Oct 12, 2018 9:22 pm

thanks for the replies onittion3 and diddly,
interesting that you think it may be something other than a carb problem. i just assumed a carb problem. i will take a look at the exhaust gasket.
hopefully a cheap and easy fix.
forgot to mention in previous posts, is 70 miles per tank full about average or is this low because of the backfire problem?

thanks
chris

Wuyang
Posts: 829
Joined: Fri May 11, 2012 10:12 pm
Rides:: None at present
Location: Sheffield

Re: innova backfire

Post by Wuyang » Mon Oct 15, 2018 8:03 am

Can't remember per tank, but at least 120mpg.

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Diesel Dave
Posts: 11055
Joined: Tue Oct 13, 2009 7:25 pm
Rides:: 1965 Enfield Diesel, 2017 Sterling, Modenas Kriss and CT200 - the only Cub left
Location: Brentwood, Essex

Re: innova backfire

Post by Diesel Dave » Mon Oct 15, 2018 8:53 am

The problem I found with an Innova is holding your nerve.

It's that point when you look down at the fuel gauge and see that little last bar flashing away; and you think "How long has that been flashing"?

It's usually 3 seconds later when the motor cuts out.

I rarely got 100 miles out of a tankful on my carbed version and ALWAYS kept half a litre in a bottle under the seat. (At least I did after the first 3 times I ran out).

I ended up refuelling at home daily from a 20 litre jerry can daily - the problem was I had a 33 mile journey to work - each way! ATEOD a CG125 made much more sense with a near 300 mile tank range.

1chris1
Posts: 15
Joined: Thu Sep 07, 2017 9:04 pm
Rides:: BMW R 1150 GS HONDA innova 2008 honda nss 300 forza

Re: innova backfire

Post by 1chris1 » Wed Oct 24, 2018 9:31 pm

hi guys,

i have changed the exhaust sealing washer but unfortunately this did not cure the problem. i have read as much as i can find on the net and watched a load of videos and i think the problem is the carburettor.
the plug is almost black, very poor mpg and still getting backfire / load popping noise on deceleration.
are there any screws on the carb i can try to adjust? or does the carb have to come off to see if the problem is internal?

thanks
chris

1chris1
Posts: 15
Joined: Thu Sep 07, 2017 9:04 pm
Rides:: BMW R 1150 GS HONDA innova 2008 honda nss 300 forza

Re: innova backfire

Post by 1chris1 » Sat Nov 03, 2018 12:16 am

got the innova running better now, took it for a long run, adjusted the idle screw down as low as possible without cutting out then adjusted the brass screw to the left of the idle screw until i got a high idle, then went back to the idle screw and adjusted it until i got a nice sounding tick over.
went back out on the road and gave the bike a good run, closed the throttle and braked to slow down and had no more backfire/popping.
hopefully it is now cured.

dmw1950
Posts: 833
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Rides:: Enfield Hunter 350/CB125F/Silverwing 600/Vespa250GTS
Location: Chatham Kent

Re: innova backfire

Post by dmw1950 » Sat Nov 03, 2018 10:14 am

On carbs you have an idle screw and an air screw, you set the idle to a fast tick over then start adjusting the air screw, screw in makes it richer and out makes it leaner. in the middle of it running rich and lean is the sweet spot, having got that, very slightly screw out until the engine speed very slightly slows. Check the throttle pick up and set back the tick over to slow idle.
You should always make adjustments when spark plug, air filter and tappets are set correct.
See a Haynes manual for spark plug colour pictures. If the air screw has been fully screwed in in the past it may be damaged as it is a tapered rod.
Always worth checking the main needle location, held by a small circlip, this can get displaced or wrongly set, usually when the throttle slide/cable is fitted.

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