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Roadster engine speed decreasing while braking

Posted: Mon Nov 16, 2020 8:05 pm
by SEC
Hoping someone might have an idea of what is causing this, the car is running amazing now except for when I go to use the brakes. As I slow down, in neutral or in gear, the engine speed begins to lower and if I brake hard enough the car cuts off (only once so far). I don't really know what is causing this issue so anything helps :) . Hopefully it isn't from all the burnouts, donuts, and fishtails I have been putting her through XD . That's what happens when you give a 20 year old a roadster hahaha. But seriously any input is welcome!! Not a major issue as car is running strong but still would like to find a fix. Didn't see any posts about this issue after looking for a little.

Thanks!
Sean

Re: Roadster engine speed decreasing while braking

Posted: Mon Nov 16, 2020 10:07 pm
by mraitch
does this happen on a FULL tank of gas??

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 7:49 am
by notoptoy
I would check float levels at the carbs

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 10:05 am
by C.Costine
How well does it idle when sitting still?

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 11:55 am
by theunz
If it is abrupt I would suspect electric short. If gradual then fuel related. Possibly gunk in tank.

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 6:41 pm
by SEC
mraitch wrote: Mon Nov 16, 2020 10:07 pm does this happen on a FULL tank of gas??
Filled tank up to check and yes it still occurs. Increased fuel mixture in carbs and it seemed to help some

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 6:42 pm
by SEC
C.Costine wrote: Tue Nov 17, 2020 10:05 am How well does it idle when sitting still?
Very well, has a slight miss when first starting but after pushing the pedal once it stops missing completely

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 6:43 pm
by SEC
theunz wrote: Tue Nov 17, 2020 11:55 am If it is abrupt I would suspect electric short. If gradual then fuel related. Possibly gunk in tank.
Very gradual, I sandblasted and sealed the tank before putting it on. I think it was fuel though but because I increased the fuel mixture and it helped some.

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 6:44 pm
by SEC
notoptoy wrote: Tue Nov 17, 2020 7:49 am I would check float levels at the carbs
One of my floats are coated in sealant after it cracked but doesn't leak at all anymore. Float levels were good but appears I need to do more guesswork carb tuning

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 7:21 pm
by jhayden
Your SRL has the free floating (not hinged) floats? Coating/repair of the brass floats is NEVER cost effective in the long run and will eventually cause problems of the type you describe. If your floats match the chambers, valves, etc.:

http://www.datsunroadster.com/PIC_PAGES ... t_info.htm

you should replace the brass with the plastic/composite floats. You will be happy that you did.

Jon

Re: Roadster engine speed decreasing while braking

Posted: Tue Nov 17, 2020 9:13 pm
by Solex68
If you need a set of floats I have them for a 1600.
$50 a pair. Plus shipping
16061-K1407 Float maybe U20.jpg
16061-K1407 Float maybe U20.jpg

Re: Roadster engine speed decreasing while braking

Posted: Thu Nov 19, 2020 2:28 am
by SEC
jhayden wrote: Tue Nov 17, 2020 7:21 pm Your SRL has the free floating (not hinged) floats? Coating/repair of the brass floats is NEVER cost effective in the long run and will eventually cause problems of the type you describe. If your floats match the chambers, valves, etc.:

http://www.datsunroadster.com/PIC_PAGES ... t_info.htm

you should replace the brass with the plastic/composite floats. You will be happy that you did.

Jon
I went to get the new floats originally from rallye but sadly they did not have any in stock. My grandfather went ahead and coated the cracked float with the sealant used for sealing gas tanks. So far it works amazing with no noticeable difference in float level, after adjusting the mixture my issue went away.

Re: Roadster engine speed decreasing while braking

Posted: Thu Nov 19, 2020 2:31 am
by SEC
Solex68 wrote: Tue Nov 17, 2020 9:13 pm If you need a set of floats I have them for a 1600.
$50 a pair. Plus shipping

16061-K1407 Float maybe U20.jpg16061-K1407 Float maybe U20.jpg
I have a 2000 body and transmission hooked up to an r16 engine lol. I appreciate the offer but I think I will ride out what I have no until I have some extra cash. (Just got a part time job finally haha)