Vortex VLR 100 - FAQ

[elmt1]

Good evening Calgarians,

I hope you are all doing well and everyone is getting excited as the racing season gets near. Over the last few weeks there have been a lot of changes here in Florida and I was very happy when Rok stepped up and added a 3 race series here in Florida. I am still a complete beginner but am learning as I go and have received a lot of help on this forum and from some locals here in Florida. One thing that I occurred to me is that there can be situations where things aren't going well and it is hard to figure out why. I am way too new at this to give advice, but i have made some observations.

One of the most common is when your motor won't start or is running poorly. Again, I am still new to give anyone any advice, but I have run into situations where my motor was hard to start or ran poorly and have received help that got things back on track. Specifically, when the motor won't start easily. There are generally 4 things that have gone wrong for me (so far). The first is that fuel isn't flowing so tapping the intake with an open hand to stop the air flow (choking it) may help. Next, it may be getting too much fuel, so open the throttle and pinch the fuel line. No spark could be that the wire to the coil is not connected or the sparkplug boot is not fully engaged. ALso, double check that the red kill button is up . Finally, difficult to start can be caused by a cracked or broken reed. If it won't turn over at all, for me it has always been that the connectors on the battery need to be pulled off and put back on.

The other frustration that I have encountered is the motor running poorly at some RPM. Usually for my kart it is in the midrange when the motor hasn't warmed up. In the cases where that has happened for me, which were usually in the morning, I turned out the high speed jet about 3 minutes and it usually fixed it and if that was the case another couple to make sure it wasn't too lean so 5-6 minutes total. When my motor is running it's best here in Florida, the exhaust temperature is between 1150 and 1180. I'm not sure if that varies based on altitude and ambient temperature since it seems to always be about 80F (27C) in the afternoon but in the morning when it is cooler, it seems like I have to go richer and as the day progresses I can put it back where it was. As the day warms up, the motor seems to run strongest if I keep the temperature at 1150-1180 by leaning it out 1-2 minutes at a time. I have been told to be careful not to go too lean and make sure that temperature is always climbing as RPM increase.

Talking with the motor builder, I think the reason my new motor seized at 2 hours was related to a few factors. I mixed the oil at 5 oz per gallon (4% which is the minimum), it was new motor, it was somewhat lean due to the change in weather. Those factors along with rain and running it at 16,400 at the end of the straight because the track was relatively dry and I geared down 2 teeth for rain. If I had a do-over, I would have gone a little richer and mixed my fuel at 5%.

This weekend another guy with a Rok VLR had the ring gear spin the woodruff key so it mat be rare but it is probably a good idea to know that a spare woodruff key and ring gear are available. Another part that wears out is the drive sprocket, for me they seem to last about 3 chains. I would stay away from the non-Rok part that you can buy, because my experience was that those break.

--David

[kolsen]

Thanks for the info and tips David, sounds like you're having a lot more fun than us.....first TnT was supposed to be this Saturday, but current forecast has snow...<sigh>

[Fred]

16,400 is way too high for these motors .. Its not making any power after 15, 600 - 15,800 and 16,000is their absolute Max although we have found it is just making noise at that RPM.... Don't try to get these to do ICA RPM you will regret it. Vortex has now discovered the batch of piston failures they were suffering was down to over revving the motor and not the piston at all.

[elmt1]

Hi Fred,

I agree that 16,400 is too high. The guy who rebuilt it was pretty adamant that anything over 16,000 is asking for trouble. I went with a rain setup and the first 5 laps in that race ended up being fairly dry, which is why I was hitting such high RPM. It was a day that saw rain off and on so those of us who don't have a team with a few people to help out, had to make a decision and the radar/clouds looked like rain to me about 45 minutes before the race so I put on rain tires, added camber, changed to wide front hubs, put a pad on the seat and geared down two teeth. The people that had support swapped for a dry setup on the grid when the previous race was won by the one guy on a dry setup, but I was pretty much stuck. The tables did turn though, and it started raining hard and the only other person on rain setup ended up making up a 1/2 lap deficit to win by 1/2 a lap.

On that track (former track now), with back-to-back hairpin turns and a long straight, it worked best to be near or at the limit of 16,000. When my motor was new, I would hit the 16,000 but as it got older I was in the 15,600 range with the same gearing. No doubt hitting 16,400 was pushing it and contributed to the motor seizing. On that day, I was running a 10/79 and on a dry day I would have run 10/77, which is a pretty tall gear for those tighter sections.

--David

[Cyruspischke]

Hey folks, I've got one to add to the FAQ. The instructions in the VLR Manual document for installing the ignition coil are wrong. The main ground wire (circled in blue) is shown connecting at the rubber isolator, which will not ground the coil properly and results in no spark. Instead, attach the ground lead to the tab above the coil mounting tab (circled in yellow) with an M6 cap bolt.

The second ground lead (circled in red) is not required, and isn't included with the package anymore.

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[JCraig83]

Does anyone have torque specs for the ROK VLR?