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Acceleration Stumbling Brat, Please Advise

acceleration brat stumble carb hitachi fuel ea81

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10 replies to this topic

#1 dartron3030

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Posted 10 April 2013 - 05:57 PM

I know it's been asked before, and I've read the responses, but I'm still at a loss. 

 

My 83 Brat has an intermittent problem of stumbling upon acceleration. It occurs whether the car is warm or cold. It seems to stumble only with slow acceleration and if I step on it, it surges and opens up, feels smooth. Doesn't seem to lack power overall and idles decently enough once it's warmed up. Stock Hitachi carb.

 

So far, in attempt to fix this issue and just because it needed it, I have replaced both fuel filters, air filter, spark plug wires, spark plugs(with new NGK, properly gapped), new distributor, put a bunch of heet and seafoam through it to clean out any gunk or water and checked for vacuum leaks by spraying starting  fluid around the intake manifold and vacuum hoses (no change in idle speed noted). I also only run 89 octane or higher fuel.

 

Im thinking it could be a partially clogged jet in the carb. Maybe some other jet opens up with more throttle and thats why it only occurs at low throttle. I haven't opened up a hitachi, but I would be willing to rebuild it if that would help. And no, I'm not getting a Weber. I've gotten 31 mpg with the Hitachi properly tuned.

 

Any advice would be appreciated. Let me know if more info is needed. Thanks yall.

 

 

 

 



#2 mikaleda

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Posted 10 April 2013 - 06:24 PM

IMHO I would say its worth rebuilding the hitachi since you don't want to go the weber route. It sounds like an internal problem in the carb somewhere, maybe sticky fuel pump or partially clogged jet.

#3 BratRod

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Posted 10 April 2013 - 07:05 PM

I would check the vacuum advance. I had this same problem with my 85 Brat

#4 dartron3030

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Posted 11 April 2013 - 02:40 PM

Thanks for the input, I'll look into the vacuum advance, but it's doubtful as the distributor including the vacuum advance is less than a year old. Any other things to look for before diving into a carb rebuild?



#5 gbianchi

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Posted 13 April 2013 - 04:58 PM

simular situation, same attempts to fix, finally replaced coil and disconnected most of epa crap, Brat is AOK  now, a little cold blooded but worlds apart from where it was. Try the coil 1st........Cheers G



#6 belacane

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Posted 13 April 2013 - 10:28 PM

simular situation, same attempts to fix, finally replaced coil and disconnected most of epa crap, Brat is AOK  now, a little cold blooded but worlds apart from where it was. Try the coil 1st........Cheers G

 

 

curious to know what you disconnected for epa crap.....



#7 JuhaKankkunen

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Posted 14 April 2013 - 02:27 PM

I had the same problem in my wagon. I did a complete rebuild....but the problem still there. Since a read this post I will try changing the coil.
Today I did a carb swap between the sedan and the wagon and both cars get better performance. I changers ten slow air bleed in the cap of one of the carbs, it was #160 and now I put a #140. Its seems to be much better!

#8 pksjeep

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Posted 14 April 2013 - 09:14 PM

Check for a fitting around the carb with a wire sticking out of the end of it. I don't remember the exact location but it think it is in the front. This is an anti diesel device. I had a spot where the wire insulation broke and caused a ground it kills the car completely. Could be yours is rattling around an causing
some issues.

Paul



#9 dartron3030

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Posted 16 April 2013 - 08:10 PM

Great ideas here, thanks. The brat is currently our of commission due to me breaking the oil pump backing plate while removing the pump to rebuild it and stop a nasty leak. I did however find the anti-dieseling solenoid to be rather loose (less than finger tight) while I was cleaning up the front of the engine.  If that turns out to be the culprit I will be very, very happy. Otherwise, I checked resistance in the ignition coil and it seems to be in spec, so...possible carb rebuild if it comes to that.

 

Juha, could you explain changing out the air bleed thing a bit more, I've yet to open up a hitachi.

 

I assume epa crap refers to the nefarious egr valve and maybe the evap canister? what else? don't tell me the cat



#10 JuhaKankkunen

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Posted 16 April 2013 - 09:45 PM

Great ideas here, thanks. The brat is currently our of commission due to me breaking the oil pump backing plate while removing the pump to rebuild it and stop a nasty leak. I did however find the anti-dieseling solenoid to be rather loose (less than finger tight) while I was cleaning up the front of the engine.  If that turns out to be the culprit I will be very, very happy. Otherwise, I checked resistance in the ignition coil and it seems to be in spec, so...possible carb rebuild if it comes to that.
 
Juha, could you explain changing out the air bleed thing a bit more, I've yet to open up a hitachi.
 
I assume epa crap refers to the nefarious egr valve and maybe the evap canister? what else? don't tell me the cat


Well....I'll try....

In my parts catalog it's appears as "Slow air bleed" #494297451. It was #160 and I put a #140 instead. It was in the top of the carb were the float is located.

Sorry about my English I'm trying to be the more clear I can.

Yesterday I changed the sparks and wires, and now the engine it's really smooth. I have new cap, rotor, condenser and pcv valve.

#11 gbianchi

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Posted 20 April 2013 - 04:11 PM

The epa junk I disconnected is, those 2 exhaust  recycle deals on both sides of the engine, the pcv valve, the egr valve, that thing that has hoses running from it up by the drivers side strut top, any hose that connected to the carb that could be disconnected and not stall the engine, if it stalled when disconnected I reconnected and plugged, any thing disconnected was also plugged, sorry about not knowing the correct terms for these things. These engines will do just fine without all that B S, also I just did what some others here on the board have done, and now I just love my Brat again! Oh ya I should also add that I am running an EA82 distsy and coil, starts on 1 or 2 sparks everytime........Cheers G


Edited by gbianchi, 20 April 2013 - 04:13 PM.






Also tagged with one or more of these keywords: acceleration, brat, stumble, carb, hitachi, fuel, ea81

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