Innova dying when throttle ripped open

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wilchatron
Posts: 158
Joined: Sun Jan 29, 2012 11:12 pm
Rides:: '04 Innova
Location: Hebden Bridge, West Yorkshire

Innova dying when throttle ripped open

Post by wilchatron » Thu Jun 21, 2018 5:56 pm

Hi all,

I'm still having what seems to be a fuel issue on my recently acquired Innova which I think is probably something relatively simple - I need the help of some engine wizards like yourselves!

The issue is this: (these conditions are exactly the same while the bike is on the stand in neutral, on the stand in gear and while riding on road) - If I quickly open the throttle fully, the bike bogs and cuts out. The throttle will operate fine if I open it at a normal acceleration speed, until I get up to around 3/4 of full throttle, at which point the engine feels and sounds like it's pushing against something and makes a "rrAAUM rrAAUM rrAAUM" sound. If I drop down to just below 3/4 throttle it performs better, but obviously I'm not 'unlocking' the full throttle potential.

what I've done so far to try and remedy it: I took off the carb and dismantled it, blew all the jets with compressed air, poked them with a single strand of copper wire, sprayed some Wynne's all over the float, body and jets and left it all for an hour or so. As far as I could see all the jets were perfectly clear before I put it back together. One thing I noticed was that when i was emptying the fuel from the carb out into a pot, a few flakes of (what seems like) thin rubber sheet came out of the fuel supply inlet pipe - their presence before and lack thereof now seems not to have made a difference to the engine performance. The float bowl had a bit of gunk in it, which I've cleared out. Some nasty greeny-brown varnishy looking stuff dripped out of some of the small holes below the choke flap when I tilted carb after the Wynne's had been in there a while.

I realise I may not have totally cleaned the carb as well as I could have. Other than this - the air filter is ok, all the breathers from the carb and airbox are clear (i can blow through them fine at least) including one that has a fat white plastic cylinder in the middle of it, the fuel seems ok (although I can't know this for sure). I haven't had the plug out yet for lack of the right sized tool (oo-err) but I do think this is more of a fuel / air issue than anything else.

https://imgur.com/a/uvIWpuI - couple of pics there of the carb for anyone who cares to look

once again, i'd be delighted if anyone has any suggestions!!

thanks

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Diesel Dave
Posts: 10527
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 dying when throttle ripped open

Post by Diesel Dave » Thu Jun 21, 2018 7:25 pm

Put a new plug in it for starters - just because it’s easy to do.

It looks like the fuel pipe may be breaking down internally or perhaps the tank cap seal may be breaking up.

If you blow backwards through the fuel line can you hear the air hissing out of the tank breather?

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onittino3
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Rides:: Honda C90, Honda innova
Location: Merstham Surrey

Re: Innova dying when throttle ripped open

Post by onittino3 » Thu Jun 21, 2018 8:45 pm

As Dave suggests look at the fuel line as a whole, Worth checking the vacuum feed petcock, if dirt as passed through the filter into the petcock this can slow the fuel down, you can take it apart and clean it out, its on the left hand side under the storage bin, just follow the fuel line, also worth replacing the in line filter again just above the petcock.

I had a simular issue with mine but another symptom of a restricted petcock was it took a while to cold start after being left, as the vacum created by kicking the bike over wouldnt supply enough fuel to start.

wilchatron
Posts: 158
Joined: Sun Jan 29, 2012 11:12 pm
Rides:: '04 Innova
Location: Hebden Bridge, West Yorkshire

Re: Innova dying when throttle ripped open

Post by wilchatron » Fri Jun 22, 2018 1:05 am

ok thanks fellas, I shall have a look at all those tomorrow, I meant to get the under-seat side panels off anyway so I may as well kill two birds with the proverbial

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Diesel Dave
Posts: 10527
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 dying when throttle ripped open

Post by Diesel Dave » Fri Jun 22, 2018 6:01 am

Also check the air filter hasn't become soggy, unless you drain the airbox regularly (there are 2 drains) it can get wet and that means no air flow.

My carb version was a bugger for doing this.

wilchatron
Posts: 158
Joined: Sun Jan 29, 2012 11:12 pm
Rides:: '04 Innova
Location: Hebden Bridge, West Yorkshire

Re: Innova dying when throttle ripped open

Post by wilchatron » Fri Jun 22, 2018 11:21 am

thanks dave, it's bone dry as the bike has been inside and unused for a good while

wilchatron
Posts: 158
Joined: Sun Jan 29, 2012 11:12 pm
Rides:: '04 Innova
Location: Hebden Bridge, West Yorkshire

Re: Innova dying when throttle ripped open

Post by wilchatron » Fri Jun 22, 2018 5:55 pm

ok, some inspection has revealed the following:

The fuel tank cap breather operates well, I could hear a solid hiss when blowing up the fuel tube thru the empty tank. The rubber seal for the tank cap is in good condition and undamaged.

There is no inline filter between the square device in the pictures https://imgur.com/a/Bwleqke (I think this is a vacuum operated fuel cock? no manual fuelcock on the bike) The cloth shrouded rubber fuel pipes along the whole fuel system are in good condition, the rubber is flexible and healthy. When I blew compressed air down them, they blew nicely and a spray of petrol came out of various breathers in the carb.

I may have made a mistake in doing so, but I've dismantled the petcock. It has a rubber diaphragm thing in it that operates when you blow on one of the pipes. One side of the diaphragm was curled upwards, meaning it wasn't sealed, but it seems to more or less seal if I press on it. The rubber here isn't in great condition, it's a bit 'old' looking.

The small metal pipe on the top part of the petcock (image 2) seems to be totally blocked, I couldn't blow through it either by mouth or compressed air. I don't know if I should be able to, though. for reference, this one had a thin, transparent yellow plastic pipe connected to it which snakes around the fuel line then connects to the manifold between carb and engine.

I hope this information is of some use! thanks again for the help so far chaps

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