Roadster engine speed decreasing while braking

General topics.

Moderators: notoptoy, S Allen, Solex68

Post Reply
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Roadster engine speed decreasing while braking

Post 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
User avatar
mraitch
Roadsteraholic
Posts: 3629
Joined: Mon Oct 02, 2006 7:03 pm
Location: Lake Balboa (SFV) - CA
Model: 1500/1600
Year: High Windshield-68-70
Contact:

Re: Roadster engine speed decreasing while braking

Post by mraitch »

does this happen on a FULL tank of gas??
Peter Harrison
1970 1600 (Stroker) - TOAD SAN (Eliza)
1970 1600 (Stock) - As Yet Unnamed
Lake Balboa (SFV) , California
User avatar
notoptoy
Vendor-Site Supporter
Posts: 9677
Joined: Fri Oct 02, 2009 2:55 pm
Location: Winston-Salem, NC and Ocala, FL
Contact:

Re: Roadster engine speed decreasing while braking

Post by notoptoy »

I would check float levels at the carbs
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

67.5 SPL311 H20 w/5 speed
65 Impala Convertible
2017 C43 AMG
C.Costine
Roadster Nut-Site Supporter
Posts: 1731
Joined: Fri Feb 13, 2015 8:08 pm

Re: Roadster engine speed decreasing while braking

Post by C.Costine »

How well does it idle when sitting still?
located in Chester NH
1967 1600 in restoration
2013 Arctic Cat F-1100 turbo
Ford F-350 6.0
Ford 9000 puller, Ford 960 puller, Ford 901show, Ford 971 worker, Oliver 70 waiting its turn
User avatar
theunz
Roadster Nut-Site Supporter
Posts: 2396
Joined: Sat May 02, 2009 1:54 pm
Location: Catoosa Ok.
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post by theunz »

If it is abrupt I would suspect electric short. If gradual then fuel related. Possibly gunk in tank.
Mike M

Old enough to know better, too old to remember why!


1969 2000 solex mine since 1972, under resurrection. (Finally resurrected as of spring 2019!)
1969 Porsche 911s -worth more, but not as valuable! Gone!
2017 Lotus Evora 400 - Oh my!!
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post 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
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post 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
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post 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.
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post 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
User avatar
jhayden
Site Supporter
Posts: 478
Joined: Tue Oct 25, 2011 4:16 pm
Location: Tyler, TX

Re: Roadster engine speed decreasing while braking

Post 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
User avatar
Solex68
Site Supporter
Posts: 2080
Joined: Fri May 25, 2012 3:30 pm
Location: Laguna Hills, CA
Model: 2000
Year: High Windshield-68-70
Contact:

Re: Roadster engine speed decreasing while braking

Post 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
You do not have the required permissions to view the files attached to this post.
Greg a.k.a SOLEX68 - http://www.datsunvents.com/
Laguna Hills, CA
68 2000
Always willing to help another Datsun Roadster owner
Pending installs: SS brake lines, Stan Stealth Dizzy
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post 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.
SEC
Roadster Nut
Posts: 34
Joined: Sun Mar 15, 2020 8:24 pm
Location: Richmond, VA
Model: 2000
Year: High Windshield-68-70

Re: Roadster engine speed decreasing while braking

Post 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)
Post Reply