Throttle lag on 68 Bonnie - Triumph Forum: Triumph Rat Motorcycle Forums
Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 20 (permalink) Old 04-14-2019, 07:27 PM Thread Starter
SuperStock
Main Motorcycle: 68 Bonneville
Senior Member
 
Theeepic's Avatar
 
Join Date: Aug 2018
Location: Southwestern Pennsylvania, USA
Posts: 237
Garage
Throttle lag on 68 Bonnie

Thought I would float this out there being it’s a rainy Sunday afternoon on the east coast of the US. A little background, 1968 Bonneville, 2000 miles on a complete stock rebuild, 932 Amels, running points, just charged battery to be sure. Took a ride last week and ran it up to about 80mph up a long smooth hill and at just a little over 80mph it started cutting out so I let off it. For the rest of the day and still it acts like there is a “dead spot” in the throttle where it lags and you need to push through that spot and then runs normal. I’d say it’s at about the halfway point or a Little less. And it feels kinda like your driving into the wind, like your pushing it a bit more than usual. So any ideas of where to start? Oh and fresh oil change to 20-50 V-twin oil if that is a factor.

Steven
Theeepic is online now  
Sponsored Links
Advertisement
 
post #2 of 20 (permalink) Old 04-14-2019, 09:54 PM Thread Starter
SuperStock
Main Motorcycle: 68 Bonneville
Senior Member
 
Theeepic's Avatar
 
Join Date: Aug 2018
Location: Southwestern Pennsylvania, USA
Posts: 237
Garage
Yes I messed up the title and it won’t let me edit.
Theeepic is online now  
post #3 of 20 (permalink) Old 04-15-2019, 12:02 AM
SuperBike
Senior Member
 
tridentt150v's Avatar
 
Join Date: Mar 2002
Location: Great Southern Land
Posts: 1,571
Garage
Starving for fuel...clean the carbies, check the flow at the bowls.

tridentt150v,
Great Southern Land.
(Where women blow and men chunder).
tridentt150v is offline  
 
post #4 of 20 (permalink) Old 04-15-2019, 01:41 AM
SuperSport
Senior Member
 
Tritn Thrashr's Avatar
 
Join Date: Jun 2016
Posts: 1,179
Could be the sort of problem oversized carburettors cause. Or, I suppose, megaphone exhausts.

How did you pick the jet sizes?

Last edited by Tritn Thrashr; 04-15-2019 at 01:57 AM.
Tritn Thrashr is online now  
post #5 of 20 (permalink) Old 04-15-2019, 09:02 PM Thread Starter
SuperStock
Main Motorcycle: 68 Bonneville
Senior Member
 
Theeepic's Avatar
 
Join Date: Aug 2018
Location: Southwestern Pennsylvania, USA
Posts: 237
Garage
Sorry for the lag time in replying, that job thing always gets in the way of bike stuff. Well got her out for a little 40 mile run, filled up the tank and it felt about 80% better. So I’m thinking bad fuel could have been the culprit? As for jet size I didn’t set it up I bought this bike “restored” so I haven’t messed with much and still have a lot to learn. Stock pipes, also what was the stock size carbs? Thanks for the replies so far. Next plan is to take back to the shop that built it along with a good bottle of Sapphire Gin for the builder himself and look over his shoulder and ask a list of stupid questions. Was going to ask about cleaning carbs, adjust valves again and timing due to popping through the carbs at times and not as peppy and the throttle once was. And thanks for the title edit also...

Steven
Theeepic is online now  
post #6 of 20 (permalink) Old 04-16-2019, 01:40 AM
SuperSport
Senior Member
 
Tritn Thrashr's Avatar
 
Join Date: Jun 2016
Posts: 1,179
Tritn Thrashr is online now  
post #7 of 20 (permalink) Old 04-16-2019, 06:09 PM
Moto Grand Prix
Main Motorcycle: 66 TR6
Senior Member
 
coloradobob's Avatar
 
Join Date: Aug 2009
Location: ft collins, co
Posts: 2,699
Other Motorcycle: 73 t150
Extra Motorcycle: TR7's, T 150's, 55 T110
Garage
Some bikes like both fuel taps open when accelerating uphill. Bob
coloradobob is offline  
post #8 of 20 (permalink) Old 04-16-2019, 08:54 PM Thread Starter
SuperStock
Main Motorcycle: 68 Bonneville
Senior Member
 
Theeepic's Avatar
 
Join Date: Aug 2018
Location: Southwestern Pennsylvania, USA
Posts: 237
Garage
Interesting Bob.... I’ll try that. One thing I noticed today before a short ride. Tickle the left carb... 1,2,3 fuel. Tickle the the right it’s 1,2,3,4,5...6 fuel. That’s with a 3/4 full tank. So I’m guessing one passage or another is restricted?
Theeepic is online now  
post #9 of 20 (permalink) Old 04-17-2019, 01:58 AM
SuperSport
Senior Member
 
Tritn Thrashr's Avatar
 
Join Date: Jun 2016
Posts: 1,179
Slow tickler action is usually caused by the roll pin being pushed too far up into the bottom of the tickler button. Sloppy assembly at the factory. Can you feel the fast tickler contacting the float earlier in its stroke?

If the float bowl is removed, the pin can be pulled down a little bit, with pliers.
Tritn Thrashr is online now  
post #10 of 20 (permalink) Old 04-17-2019, 03:58 AM
Formula Extreme
Main Motorcycle: 2001 SV650S
Senior Member
 
Join Date: Jan 2014
Location: Honolulu, USA
Posts: 563
Other Motorcycle: 1967 T100R
Extra Motorcycle: 1986 CB450SC
I've certainly had flat spots in carbs before - usually caused by running lean on purpose at certain throttle positions due to US EPA regulations. A little rejetting usually sorts that out.

Also had a bike cut out on an LA freeway due to high speed fuel starvation. Great fun.

In your case, you say that it started during hard running and then stayed that way. I kind of wonder if you sucked up some particle of dirt, and it's worked its way loose now?
JSurace is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options
All posts must adhere to Forum Rules

Register Now



In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Quick Throttle Mod DEcosse Speed Triple Forum 151 01-23-2019 01:36 PM
Installing new throttle cables on EFI Bonnie Bobajobbob Air Cooled Twins Technical Talk 5 06-11-2018 06:02 PM
EFI Public Service Announcement - Coughing? Poor Throttle Tip-In? Poor Idle? dualshowman Air Cooled Twins Technical Talk 11 10-11-2017 09:33 PM
The Bonnie Tales #2: Henry & Ken Bonnie06Tangerine Ride / Trip Reports 12 04-08-2010 07:12 PM
"The Bonnie Tales" #1: The Sunday Roast Bonnie06Tangerine Ride / Trip Reports 20 08-05-2009 06:12 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome