Finding Intake Manifold Air Leaks

Print
User Rating: / 24
PoorBest 
Written by David Tise (Bulldog)   
Friday, 11 June 2004

David is a Technical Moderator, for Baron's Custom Accessories Technical Forum

Your engine had been running fine. Recently it has started running poorly or backfiring, maybe when its warm, maybe when its cold or sometimes the problem just seems to come and go. The problem shows signs of both a rich and lean running carburetor. You have done the obvious like change jets, replace spark plugs, check plug wires and replace your air filter element, but the problem persists. You and your mechanic are quite frustrated because you can't seem to identify the problem.

Erratic symptoms like these can be the sign of an air leak at the intake manifold or carburetor.

The design of the Road Star engine and the intake manifold make it prone to air leaks. Improper installation and age are two major contributors to the condition. Symptoms usually develop just after working on or around the carburetor.

Finding an air leak at the manifold is simple. All you need is a can of penetrating oil (like WD-40) with the extended nozzle attached. With the engine idling, direct a heavy spray of  the penetrating oil at the manifold gasket area and base of the carburetor. When the spray hits the area leaking, there will be a distinct change in the sound of the engine. If the air leak is major, the change in sound will be quite obvious. Smaller leaks may only create minor changes in the sound.

The engine temperature need to match the times the problem most frequently occurs. If you accidentally spray the exhaust system, you may get a little smoke. The penetrating oil can be cleaned up by washing the bike after the engine cools.

The CV carburetor has one additional area that can create problems. The slide has a neoprene diaphragm at the top. If the diaphragm is installed improperly or develops cracks, an air leak will occur. Problems are most likely to develop just after re-jetting or  making modifications to the carburetor. Make sure you properly install this diaphragm after upgrading your CV carburetor. The diaphragm must be properly seated or an air leak will develop.

Using this information, you now have the means to identify the cause of may baffling performance problems on your engine.

Bulldog

Barons Custom Technical Form Staff



Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

Discuss this article on the forums. (0 posts)


DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.


Quote this article on your site | Views: 36275

  Comments (3)
Written by MickeyGee66, on 08-13-2015 13:35
The method of using WD40 to find an air leak leaves an oil film on parts that u do not want oil film on! Use a propane torch with the valve slightly cracked (unlit of course) and pass it around all parts of the intake system while the bike is idling. If there is an air leak when u pass the propane nozzle over where the leak is RPM will pick up a bit ! DO NOT worry this will not harm ur engine or anything else! I was only 20 years old when I learned this trick from a "grey beard"................ NOW I AM a grey beard & passing the info to younger riders !!!! I have used it many times on bikes, cars & even diesels and it WORKS + no oily film on anything !!!
42 mm mukini
Written by lunchboxx, on 11-22-2008 15:58
I recently put a 42mm mukini on and got rid of the fuel pump. The bike runs good but I now have a popping when I downshift or let off the throttle . Got any tips for me?
2000 ROADSTAR BACKFIRING AT AIR FILTER
Written by WICHI54, on 04-05-2007 15:50
CHANGE PLUGS CHECK ELECTRIC CONNECTORS FUEL PUMP WORKING 
LOTS OF BACKFIRING UNABLE TO RIDE THE BIKE 
DOES ANYONE KNOWS WHAT MAY CAUSE THIS PROBLEM 
I RODE THE BIKE FOR AN HOUR IT WAS WORKING JUST FINE 
PARKED FOR A WEEK WHEN I TRIED TO STARTED FELT AS IF HAD THE CHOKE COMPLETELY CLOSED 
RUNNING VERY POOR I NEED HELP ASAP THANKS 
:upset :upset

Only registered users can write comments.
Please login or register.

Powered by AkoComment Tweaked Special Edition v.1.4.6
AkoComment © Copyright 2004 by Arthur Konze - www.mamboportal.com
All right reserved

 
...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... -->



The Road Star Clinic is a collaborative community of riders who archive and publish user contributed technical data about Yamaha Road Star motorcycles.

We also sponsor the creation and support of other community websites similar to our own. Inquiries about availability of a website for your community can be submitted to us via any "Contact Us" option on the Clinic.

Copyright 2003-2007 Road Star Clinic and its respective authors. Road Star Clinic is sponsored by the folks at MLSHomeQuest.com.