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backfiring witnessed on top of intake boot

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backfiring witnessed on top of intake boot

PostAuthor: alaska1 » Wed Mar 13, 2019 1:31 pm

So this bike started up and proceeded to blow chunks of dog food out the tailpipe. My question is whether or not it is possible that mice have plugged up the exhaust with dog food? It started strong with the choke on, would not run with choke off. I witnessed a small flame out of the top of the intake boot when backfiring. I have ordered new boots but am afraid that I may blow out the new one if the tailpipe is clogged. Perhaps the only problem is a bad vacuum leak through the boot. Suggestions?

Thanks

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Re: backfiring witnessed on top of intake boot

PostAuthor: Flyingdog » Wed Mar 13, 2019 3:02 pm

alaska1 wrote: Suggestions?


Cat for the mice.
Dog for the food.
:bg:
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Re: backfiring witnessed on top of intake boot

PostAuthor: alaska1 » Wed Mar 13, 2019 4:17 pm

okay, update. Went out today and it started fine but runs a bit like crap. Seems to be fine on the exhaust.

Dogging on throttle, wondering what is priority, air fuel screw or balancing carbs?

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Re: backfiring witnessed on top of intake boot

PostAuthor: mark75 » Wed Mar 13, 2019 4:28 pm

priority: idle, take throttle, performance ...

my guess is varnish from storage.
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Re: backfiring witnessed on top of intake boot

PostAuthor: Flyingdog » Wed Mar 13, 2019 5:30 pm

:yup:

Be my suggestion too...plus a good cleaning of the carbs probly wouldn't hurt. Running on choke only is usually the first sign your pilot circuit is plugged (among others). Was this thing stored long? Check "all" wire connectors (clean..shiny..tight) specially coils' primary wires, air cleaner clean, no vacuum leaks and fully charged battery<---Mark, you feel OK?.. that's usually your first requirement. :bg:
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Re: backfiring witnessed on top of intake boot

PostAuthor: alaska1 » Wed Mar 13, 2019 10:01 pm

Yes, the carbs were totally cleaned, that was the first thing. All hoses replaced and rebuilt the petcock.I t holds idle fine now and revs up when not under load. Running down the street it backfires a bit and has no power. I noticed that the back intake boot port was open so I plugged it. Didn't seem to change much at all. Sprayed starter fluid around intake boots and really no change. turned the jet for the rear cylinder all the way in and all the way out and it didn't seem to change much. When I adjusted in the the front one, it backfired when increasing rpm so I backed it off to two and a half turns.

I need to ask as I was unable to find it again in the forum, is it needle, spring, stainless washer, rubber o ring? this is on the pilot jet, of course. Hitachi carb on this 86.

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Re: backfiring witnessed on top of intake boot

PostAuthor: Flyingdog » Thu Mar 14, 2019 2:32 am

alaska1 wrote:is it needle, spring, stainless washer, rubber o ring? this is on the pilot jet


Yes, that's the correct order. If ya replaced the 0-ring, make sure the old one was removed. You'd be surprised how often this is over looked, usually cuz the old one didn't 'fall' out. Sometimes the old one gets kinda wadded up or really jammed in there and can't be seen, until ya get in there and dig it out.

alaska1 wrote:noticed that the back intake boot port was open so I plugged it. Didn't seem to change much at all. turned the jet for the rear cylinder all the way in and all the way out and it didn't seem to change much.

alaska1 wrote: When I adjusted in the the front one, it backfired when increasing rpm so I backed it off to two and a half turns.


Whelp..that right there should tell ya. Something is still not right. They "both" should effect their respective cylinders. Doesn't necessarily mean both pilots will have the same number of turns. The pilot circuit is absolutely necessary for starting, idle and a smooth transition from off idle onto the jet needle.
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