'76 idle bogs when blipping throttle

Discuss everything about Honda GoldWing. Feel free to ask any question related to GoldWing.

Moderators: CYBORG, Oldewing, robin1731, Forum Moderators

Post Reply
jimbonaut
Chrome Member
Chrome Member
Posts: 121
Joined: Sat Dec 19, 2020 3:08 pm

'76 idle bogs when blipping throttle

#1

Post by jimbonaut »

Feels like I'm getting closer. When warm, the engine idles fairly well at around 1100 rpm. Takes a while to warm up admittedly, and I need a lot of choke and gentle throttle encouragement to get it to idle all on its lonesome. It's getting a bit cold in my garage however these days (not much above freezing the last few days and only getting colder from here on in) so maybe that has something to do with that.

My question for today is, why does the idle bog when I blip the throttle but rpms go up smoothly when I roll on the throttle? I've checked the plugs (somewhat sooty) and my mixture screws are at the three turns out recommended setting. No huge amount of smoke belching out of the exhaust when I blip the throttle (or roll on it), stock carb set-up (rebuilt with Randakks kit), new air filter. My guess the bogging is caused by a rich mixture, but it's a guess at best. Here's a vid -

https://www.youtube.com/watch?v=HBEg1pmc9u0

I tried turning the mixture screws a half turn in each, to no discernible effect.

Thanks for the help with my previous question regarding the valve check procedure. Getting the valve clearances in spec definitely helped the flaring idle (rpms were going up all by themselves), now the idle is much better.
User avatar
gltriker
Honored Life Member
Honored Life Member
Posts: 5053
Joined: Fri Sep 24, 2010 9:11 pm
Location: central NY State

Re: '76 idle bogs when blipping throttle

#2

Post by gltriker »

Cold weather cold engine.
Betcha if you remove the air filter cover and look into the " plenum" when you blip the throttle, you might hear(pop), and less likely, see (flame), an off-idle backfire into the plenum from at least one carburetor. A *lean* fuel mixture ratio, intake backfire.
Remember, the carburetors are correctly, engine idle speed synchronized when the entire engine (including carburetors) is at completely full operating temperature. Mike Nixon gave the recommendation to set each carburetor's air/fuel pilot mixture screw at 3 turns out from seated.
In a strictly layman's interpretation I would presume to 'explain' it; one incidental benefit of that richer air/fuel pilot idle mixture is to crudely - especially when *blipping* an unloaded GL1000 engine - simulate the contribution an integral accelerator pump provides to address engine hesitation which usually accompanies rapid throttle opening;
In gear, pulling away from curb, a dynamically loaded engine is another 'story.' ;) To the point... blipping of throttle is not useful then.

If your synchronizing gauges were all hooked up, a *lean* fuel-to-air ratio backfire occurring in an individual carburetor throat will be displayed as an abrupt air pressure spike from that one's intake manifold synchronizer adaptor. :shock:
Last edited by gltriker on Thu Nov 17, 2022 1:40 pm, edited 15 times in total.
Cliff (74yrs ;) )

Keep your eyes and ears open and you'll learn something new, everyday. tumb2

New users please visit our "Shop Talk" for common tips and help: <---jdvorchak
http://www.ngwclub.com/forum/page/ST
^^^^^^^click up here^^^^^ :oldies

RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi tumb2
"Can't see the paint when your looking thru the handlebars..........." -Oldewing ;)
"I'd rather Ride than Shine" -RAT tumb2 Me Too!!

Cliff

'75 GL1000 home built trike; http://www.ngwclub.com/forum/viewtopic.php?f=30&t=39996
October,2017 BOTM :shock: https://nakedgoldwingsclub.com/forum/page/Welcome

previous rides:
1953 H-D Servi-car, naked, 1969-1978 (serial#53G1559 committed to memory!)
1980 CB900 Custom (triked) 1997-2003 .... R.I.P.
User avatar
pidjones
SUPER BIKER!!!!
SUPER BIKER!!!!
Posts: 3237
Joined: Wed May 22, 2013 4:06 pm
Location: East TN

Re: '76 idle bogs when blipping throttle

#3

Post by pidjones »

Long intake runners make for long warm-up times. It will improve as the carb tune gets better. Bogging on blipping is often an indication of lean. I can't remember if the '76 is one with carbs particularly prone to this. There is an easy fix for those that are (visit Randakks blog pages).
"Love 'em all.... let God sort 'em out!"
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
cfairweather
Silver Member
Silver Member
Posts: 683
Joined: Sun Apr 13, 2014 10:37 pm
Location: Cheyenne, Wyoming

Re: '76 idle bogs when blipping throttle

#4

Post by cfairweather »

That article basically says to remove the size 115 pilot jets from the 4 brass elbows. Obtain smaller air jets, size 60, and drill them out with a #59 drill bit for a 76 model. This will make the idle richer and solve the off idle issue. It will also make the bike easier to start.

Here is a link to entire article:
https://www.randakksblog.com/how-to-cur ... flat-spot/
jimbonaut
Chrome Member
Chrome Member
Posts: 121
Joined: Sat Dec 19, 2020 3:08 pm

Re: '76 idle bogs when blipping throttle

#5

Post by jimbonaut »

Well, there it is. Thanks for the insight and links - seems like the "off-idle" situation is a quirk these bikes are known for. Very interesting read on how to address it by soldering closed the idle air jets and then drilling them out with a #59 micro bit to enrichen the idle circuit. I'll give it a try and report back.

Also good to learn more about the longer-than-usual choking and slow warm-up times on this bike too. Will be interesting to see what effect drilling out those jets will have.
redglbx
Gold Member
Gold Member
Posts: 1116
Joined: Tue Jun 02, 2020 8:39 am
Location: NW Indiana,

Re: '76 idle bogs when blipping throttle

#6

Post by redglbx »

I’m not a fan of drilling jets, nearly impossible to make them all the same. I just buy new #110 jets from either Jets-R-Us or usually PJ’s Motorsports. You get much more consistent results. I also replace the fuel jets, the primary main which on your 76 is a #62 stock with a #65 and the stock #120 secondary mains with #115’s . These changes provide a much flatter fuel curve richening up the super lean low end and leaning out the pig rich top end. All bought through PJ’s.

The off idle (bog) leaness that you are seeing is the result of the #62 primary mains and the #115 air jets (in the brass elbows). I have found a lot of improvement with the jet changes I mentioned above BUT will add that these are vacuum slide carbs without an accelerator pump so a little bit of this is to be expected.

Also, as mentioned above a good, precise sync of your carbs will help as well. What are you using for ignition ? Stock points & coils ? Really lean jetting like the stock jetting is hard for a stock barely adequate ignition like the gl has.

I will add that once you go for a ride that your GL as is would run just fine under normal load !
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
cfairweather
Silver Member
Silver Member
Posts: 683
Joined: Sun Apr 13, 2014 10:37 pm
Location: Cheyenne, Wyoming

Re: '76 idle bogs when blipping throttle

#7

Post by cfairweather »

I buy cheap third party kits just to get the size 60 air jets. It is easy to drill them because they already have a starter hole. Just hold the jet with two fingers and push it into the bit. They come out perfect every time for me and the jets work as well as any factory Kehin jet made. The pilot jet is the primary cause of the problem he is having and it needs to be smaller to richen up the low RPM mix. The mains do play a small part, but they come into play much more at higher RPMs.
If I had a wide open issue, I would be looking at the main jet circuit, not the pilot jet circuit even though it might play a minor role. I am not saying your primary and secondary jet suggestions don't help, but in my opinion, he first needs to get size 60 air jets and get his drill out. I have found it is much easier to drill new third party size 60 jets rather than soldering the original 115 jets.
jimbonaut
Chrome Member
Chrome Member
Posts: 121
Joined: Sat Dec 19, 2020 3:08 pm

Re: '76 idle bogs when blipping throttle

#8

Post by jimbonaut »

I like that suggestion, especially knowing it's a tried and tested method. Before I go whaling on the jets I have, I'll order some #60's from PJ Motorsports and drill those out instead and take it from there.

The top end on this bike is an unknown to me, I've never ridden it. Great suggestions about replacing the mains, but I'll wait and see what gives when I finally get the old girl on the road. As for the carb synch, that's been done many times now (with varying degrees of success - largely down to poorly adjusted valves) but they're now pretty much dialled in, and always synched when the engine is as warm as I can get it simply by throttling it some up on the table. Ignition is stock.

If anyone who's ordered from PJ's before can send me a link to the air jet in particular I need that would be great (I know where it is in the carb, I just want to make sure I order the correct one). Thanks gents as always.
cfairweather
Silver Member
Silver Member
Posts: 683
Joined: Sun Apr 13, 2014 10:37 pm
Location: Cheyenne, Wyoming

Re: '76 idle bogs when blipping throttle

#9

Post by cfairweather »

Send me your address and I will send you 4ea size 60 jets. You can send a PM if you like. I will even drill them for you if you like.
jimbonaut
Chrome Member
Chrome Member
Posts: 121
Joined: Sat Dec 19, 2020 3:08 pm

Re: '76 idle bogs when blipping throttle

#10

Post by jimbonaut »

cfairweather wrote: Tue Nov 15, 2022 9:40 am Send me your address and I will send you 4ea size 60 jets. You can send a PM if you like. I will even drill them for you if you like.
Outstanding, that's very kind of you indeed. The benevolence of strangers...there's nothing like it. I'll pm you now
User avatar
dontwantapickle
Silver Member
Silver Member
Posts: 946
Joined: Fri Oct 13, 2017 9:26 pm
Location: Colorado

Re: '76 idle bogs when blipping throttle

#11

Post by dontwantapickle »

After the jet change, please report the results.
jimbonaut
Chrome Member
Chrome Member
Posts: 121
Joined: Sat Dec 19, 2020 3:08 pm

Re: '76 idle bogs when blipping throttle

#12

Post by jimbonaut »

dontwantapickle wrote: Tue Nov 15, 2022 1:40 pm After the jet change, please report the results.
Absolutely I'll do that
User avatar
pidjones
SUPER BIKER!!!!
SUPER BIKER!!!!
Posts: 3237
Joined: Wed May 22, 2013 4:06 pm
Location: East TN

Re: '76 idle bogs when blipping throttle

#13

Post by pidjones »

And, if you haven't already - CHANGE YOUR BELTS!
"Love 'em all.... let God sort 'em out!"
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
redglbx
Gold Member
Gold Member
Posts: 1116
Joined: Tue Jun 02, 2020 8:39 am
Location: NW Indiana,

Re: '76 idle bogs when blipping throttle

#14

Post by redglbx »

Just to clarify,, the reason I don’t drill jets is because the size of the hole is just a small part of what meters the fuel. The length of that hole also has a large effect on fuel metering as does the surface finish, and the entry and exit corners of that hole.

This all is why Holley carb jets are sized by flow and not size, I believe Keihin jets are sized the same way but I am not positive of that, Holley jets I am. I do not drill jets, I also don’t use them from the cheap Chinese “eBay” rebuild kits. My .02
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
cfairweather
Silver Member
Silver Member
Posts: 683
Joined: Sun Apr 13, 2014 10:37 pm
Location: Cheyenne, Wyoming

Re: '76 idle bogs when blipping throttle

#15

Post by cfairweather »

The pilot jets are air jets, not fuel and the air passes through those brass elbows into the carb. You could install the jet inside the rubber tubes and it would work the same because the jet only limits the amount of air entering the carb. Buying a high quality Kehin jet does not guarantee you have an accurate jet. I have measured Kehin jets that were way off from the stamped size, but they are usually correct. You can only be confident when you use a gauge to verify the size. One of the recommendations in the article is to use solder, which I don't personally like, but the goal was to close the hole and re-drill it to the smaller size. The shape of the jet is definitely changed with the solder, but it does not matter.
Post Reply
  • Similar Topics
    Replies
    Views
    Last post

Return to “GoldWing Tech Discussions”