VLR trouble shooting item

Forum rules
The forums are a place for open discussion of karting topics. Please respect the opinions of others. No name calling, abuse, bashing etc. of any sort will be tolerated and offending posts will be removed and offenders sanctioned at the discretion of the webmaster or the executive. All posted materials, text, etc. become the property of the CKRC and may be displayed or removed at the discretion of the CKRC.
Post Reply
User avatar
John Kwong
Posts: 1313
Joined: Wed Sep 24, 2008 8:00 am
First Name: John
Last Name: Kwong
City/Town: Calgary
Location: Calgary
Contact:
Contact John Kwong

VLR trouble shooting item

Post by John Kwong »

Hi All,

Today we had a new VLR motor that would idle but wasn't able to rev under higher throttle application. After diagnosing everything from the reeds to rebuilding the carb, changing plugs and checking the wiring harness the culprit was the Carburetor Intake Manifold(item 30).
vortex-vlr-carb-manifold.jpg
vortex-vlr-carb-manifold.jpg (67.21 KiB) Viewed 2149 times
The hole by the red arrow (in photo) feeds crankcase pressure to the carburetor pumper with each stroke of the crankshaft. The carburetor was getting enough pulse pressure to run at idle but under higher RPMS the motor would starve for fuel. In this case there was a manufacturing defect that did not have the tunnel machined out completely. Once this defect was identified and the tunnel was cleared the motor ran as normal.
VLRcases.JPG
VLRcases.JPG (106.46 KiB) Viewed 2149 times
Red arrows above and below show pathway of case pressure pulses.
VLR Carb back.jpg
VLR Carb back.jpg (64.15 KiB) Viewed 2149 times
John Kwong___CIR Realty___403-714-5583
www.johnkwong.ca
http://kartopractor.weebly.com/
Top
phil
Posts: 411
Joined: Mon Sep 29, 2008 9:52 pm
First Name: phil
Last Name: haggerty
City/Town: high river

Re: VLR trouble shooting item

Post by phil »

How long did it run without sufficient fuel? I would be concerned about the bottom end not having been lubricated enough, and may lead to pre-mature bearing failure.
Top
User avatar
Fred
Posts: 1212
Joined: Thu Sep 04, 2008 10:52 am
First Name: Fred
Last Name: Causer
City/Town: Calgary
Location: Calgary AB
Contact:
Contact Fred

Re: VLR trouble shooting item

Post by Fred »

It didn't ! Because it wouldn't clear itself it loaded up the bottom end and when we took the exhaust off it was swimming in oil ! I have sent a message to ROK Canada and ROK USA to make sure they know of the problem in case we have a Warranty issue.
Top
elmt1
Posts: 51
Joined: Thu Sep 12, 2019 4:58 pm
First Name: David
Last Name: Morris
City/Town: Whitefish

Re: VLR trouble shooting item

Post by elmt1 »

The same thing will happen if you get the gasket installed upside down. In other words, if the hole in the gasket isn't aligned with the hole in the intake, it will do the same thing - it will start and run but won't rev up. I found this out when I had to remove my carburetor and reeds for inspection after a heat race and then before the main race, my engine wouldn't run right. Fortunately, the engine builder knew exactly what I did wrong and helped me rotate it 180 degrees.
Top
Post Reply

Return to “ROK VLR 100”