CKRC Forums

Welcome to the VLR forums and hopefully you will find this post informative.

As the Vortex VLR 100cc engine is fairly new there’s not a lot of specific information around about it. If you’re familiar with 2-stroke or 100cc classes some of this might be transferable, but in case you’re new to both, we thought this would be a good start to help build your comfort level with the class.

This post is a work in progress, if you have any additional information to add please let me know. I've been gathering information from different sources I assumed others would have similar questions so decided to post this...

Disclaimer: This post is by no means the authority on below said topics, more of a guide or starting point to help our members. if you do spot any inconstancy's please to let us know.

Vortex Website
http://www.vortex-engines.com/motori-rok-vlr_en.php

Attached files Videos
Vortex VLR disassembly
https://youtu.be/VWAsbEEWN_Y
Vortex VLR assembly
https://youtu.be/a33VuFWoOso

Miscellaneous
• Good idea to put a bead of silicon on the exhaust springs to reduce the vibration which will start to wear the spring. Alternatively you can purchase insulated springs (has rubber cover to reduce vibration)

Fuel Mix
• Between 4% and 5% mix is recommend on pump gas (club regulations)
• 20:1 or 5% would mean 50cc of oil for every 1000cc of fuel (50ml/litre)
• 25:1 or 4% would mean 40cc of oil for every 1000cc of fuel
• Castor oil is generally not recommended to be used

Spark Plugs
*ROK USA define EG plugs only in their rule book. EIX also work but not regulation*
• NGK BR9EG
• NGK BR10EG


Clutch
• The type used is a dry centrifuge clutch which should not require a lot of maintenance
• A spray of Brakleen clean is recommended. Ensure you grease the needle bearing prior to re-assembly
• The use of an impact gun can be used to remove and install the clutch without requiring a special tool
• Briggs clutch maintenance is very similar if you are familiar with that process
• *PSA* never run the engine without the clutch housing on. The pads will separate as there is nothing to stop them.
Carburetor
• Settings are generally measured in Turn outs (T.O) or "minutes"
• Factory settings at 1TO on High and Low
• For the most part you should not need to adjust these on track unless you have experience doing so.
• Recommendation to have a carb pop-off gauge to test periodically and after service
• In testing after a year of usage, the carb screens looked good when using a filter in the airbox.
• If you run your carb through a cleaner and remove the needles. The low speed needle is the one with the longer tapered point
• Careful not to over tighten the top fuel strainer cap as over time this can crack and lead to leaking [noted in the "howto service your carb"
Setting Tillotson Carb Popoff - https://www.kartpulse.com/article/60/se ... arb-popoff
Tuning by ear - https://forums.kartpulse.com/t/tillotso ... ngs/3748/6
How to service your carb - https://tillotson.ie/wp-content/uploads ... son-LD.pdf
Carb replacement parts
• Full repair kit RK-8HW
• Gasket kit only DG-1HW

EGT
• Optional but recommended to run an EGT to ensure optimal performance and engine life
• 1100 target temp range
• Ensure that your EGT is at the right depth to get accurate reading

Starting
• Electric start. Reminder to keep your battery on a tender if you’re not going to be using it for a while. (winter)
• The Red button has 2 positions. Button poking OUT, is ignition ready and button depressed IN is circuit broken motor kill. Leave in the IN position when not running but make sure it is in the “OUT” position or the motor will not start.
• You may need to choke the engine to start it, do this by covering the air box holes and pressing the start button
* in the event of a starter failure its good to first check and replace the brushes. adding a dab of silicon can improve lifespan. Replacement brush part number W941/ROK-2019.
ROK USA defines that you need to use original buttons in the regulation. replacement part numbers: W2115/1ROK & W2116/ROK

Engine Break-in
• 5 minutes on stand at 0 to full throttle blips.
• Then on the track 10 minutes first time maximum 10,000 rpm, then coast 3 seconds. Repeat the whole way around.
• Take a 10 minute break and repeat to 12,000 rpm.
• Take a 10 minute break and repeat to 14,000 rpm.

Thanks for putting this out there. It is really helpful. You have some great information here and it covers quite a bit. I didn't notice it before, but I just read ROK VLR Manual in your post and learned that the shiny clip is to make sure the starter relay doesn't work its way out

My experience with running the VLR this year

The motor that Jimmy got me showed about 11 hours on the timer. He said the timer was put on after the motor had a great deal more hours on it. It had 14.5 hours on it when I gave him the motor back. I ran one club race and 5 ROk Cup events at CKRC. I always had the green "L" shaped exhaust temp sensor on it and basically adjusted the carb 3 times during the season while on track. With the exhaust temp gauge, you always know exactly where the motor is tuning wise and the Tillotson carb is very consistent and easy to use. I serviced the clutch when I got the motor but never looked at it again all season. I ran a foam air filter inside the airbox to protect the motor which kept the carb and motor nice and clean. I only needed one chain and changed the rear sprocket once when we changed the track direction. For the first couple races, I used the leftover Vega Green tires that I had from last year that had about 50% life in them left and then only used one new set during the year which have about 60% life left in them now. The motor used Premium gas and not a VP type race fuel so that was economical. The mix ratio was about 20:1 vs 40:1 for my Rotax, so it used a fair bit more oil but pretty marginal on the cost scale.
Overall, this has to be one of the easiest to run and economical race engines that I have ever run. At about 21 horsepower, the cost to speed ratio cannot be beat and has the reward of more top speed and 2 cycle acceleration. I thinkg this is perfect for a racer who wants more speed than a Briggs but Rotax is too fast or expensive, the VLR class fits right in the middle for speed and initial cost but with running costs about the same as the Briggs.

John K

Nice write-up John. Thanks. This certainly sounds like the class for me. I'm looking forward to it.

Good evening Calgarians,

I recently moved to Ocala Florida and have been using my kart quite a bit more than was possible in Montana. I did run into a problem last weekend when my kart wouldn't run over 14,000 RPM but seemed OK up to about 12,000 RPM. It turns out I had sucked up a number of knats into the airbox that were in the carburetor. Needless to say, I am now looking for a good filter. The faq describes an AIR1012:20 Deg Air filter and John mentioned a Foam filter. Either way, do you have any more guidance on how those are installed?

Thanks!

elmt1 wrote: Mon Jan 11, 2021 6:29 pm Good evening Calgarians,

I recently moved to Ocala Florida and have been using my kart quite a bit more than was possible in Montana. I did run into a problem last weekend when my kart wouldn't run over 14,000 RPM but seemed OK up to about 12,000 RPM. It turns out I had sucked up a number of knats into the airbox that were in the carburetor. Needless to say, I am now looking for a good filter. The faq describes an AIR1012:20 Deg Air filter and John mentioned a Foam filter. Either way, do you have any more guidance on how those are installed?

Thanks!

Hey!

Remove the stock rubber housing on the air box and then you really just shove the new filter into the box. you can pivot the new rubber housing to ensure the airbox is sitting the right way. It may seem that the filter will be hitting the intake cones but it will be fine.

side note; may want to check your reeds to see if there is any damage, doubtful from knats but something to check. as well you may need to change your carb settings as your at a different elevation than Montana, recommend starting at factory.

Thanks for clarifying how that is installed. I will put in an order for that filter and try it out. Come to think of it though, the knats were in the wet side of the carburetor so they must have made it into my fuel tank. Maybe they crawled into my fuel can but I don't think I ever left it open. There were half a dozen dead knats on the fuel screen. I did reset the high and low screws when I got here and it seems to run great unless there are bugs in the fuel. Strange thing is that there was a guy testing a brand new Rotax DD2 and he had a similar problem on the same day and he bought C12 from them also so maybe those knats are attracted to the smell of lead and flew into the pump nozzle. He said he had checked his wiring and cleaned his carburetor and it fixed it but didn't mention seeing any bugs. I used to strain my fuel through a paint strainer so maybe I should start doing that again.

--David

You could also stick an inline filter in as well...just make sure it's a god quality one.

Keith

Good Morning, I hope all is well in Calgary and everyone is getting ready for next season.

When should you rebuild a motor? From what I have read in this forum, you can go years. There aren't really any ROK VLR people here in Ocala, but talking to the KA people that come here to practice from New Jersey, they say to be competitive you have to rebuild frequently, however they seem to have unlimited budgets.

Since getting to Florida I have been going to the track 3-4 days each week so 9 long days and 7 short days. I have noticed that my new motor is now about where my original motor was as far as performance. I can't hit the same speeds I did when the motor had about 4-5 hours. I don't have an hour meter on my kart but I have run about 29 gallons through it since getting here and had put 7-8 gallons through it in Montana. I am guessing it is about 2 gallons an hour based on doing about 140 laps here on a weekend day and 70 on week day evenings with laps taking about .40 seconds. What I have found is that rebuilding the carburetor helped and I believe I have tried a number of gear ratios. At 5 hours, it was pretty easy to hit 15,500+ on the straight here with a 10 - 78 now I can't hit that RPM with a 10 - 80.

I feel like I have been pretty good at keeping up with clutches, chains, sprockets, drivers, tires, alignment, etc. so I think the motor is just getting older. I have cleaned off the carbon a few times and the barrel looks pretty smooth with no evidence of cross hatching now, but I didn't really look closely when it was new so I am not sure how to tell where I am at and I don't have a bore gauge to check it. I haven't found anyone local that rebuilds ROK motors, which is strange because the importer is an hour away. I may need to ship out my motors to have them rebuilt but I would rather walk it in somewhere.

elmt1 wrote: Tue Jan 26, 2021 8:31 am Good Morning, I hope all is well in Calgary and everyone is getting ready for next season.

When should you rebuild a motor? From what I have read in this forum, you can go years. There aren't really any ROK VLR people here in Ocala, but talking to the KA people that come here to practice from New Jersey, they say to be competitive you have to rebuild frequently, however they seem to have unlimited budgets.

Since getting to Florida I have been going to the track 3-4 days each week so 9 long days and 7 short days. I have noticed that my new motor is now about where my original motor was as far as performance. I can't hit the same speeds I did when the motor had about 4-5 hours. I don't have an hour meter on my kart but I have run about 29 gallons through it since getting here and had put 7-8 gallons through it in Montana. I am guessing it is about 2 gallons an hour based on doing about 140 laps here on a weekend day and 70 on week day evenings with laps taking about .40 seconds. What I have found is that rebuilding the carburetor helped and I believe I have tried a number of gear ratios. At 5 hours, it was pretty easy to hit 15,500+ on the straight here with a 10 - 78 now I can't hit that RPM with a 10 - 80.

I feel like I have been pretty good at keeping up with clutches, chains, sprockets, drivers, tires, alignment, etc. so I think the motor is just getting older. I have cleaned off the carbon a few times and the barrel looks pretty smooth with no evidence of cross hatching now, but I didn't really look closely when it was new so I am not sure how to tell where I am at and I don't have a bore gauge to check it. I haven't found anyone local that rebuilds ROK motors, which is strange because the importer is an hour away. I may need to ship out my motors to have them rebuilt but I would rather walk it in somewhere.

Hey David, not to sure if you got my email but a high-level summary of things to check.
Spark plug - check to see if its not fouled
Reed - check to ensure its not damaged or fraying
Carb - ultrasonic clean if possible, check the jet isn't clogged, check pop-off. check/replace filter kit. The white plastic top tends to crack if over tightened which may cause a leak.
Fuel filter if inline, ensure its not clogged
Gearing, try going back to your old gearing just to validate. if you have lap times to compare as well.
Mychron (or equiv). insure that you have the right rpm range set.

Dan
Edit: without diving into the compression side of things, check the above.