[Samir Shah]

Thanks TJ. It’s good to hear that the cheek pads are replacable. We kept the Vector 2 (small) going by doing just that (as well as the head liner), but its just a tad small now, as he grows.

Does the interior padding have foam that can be removed to further optimize the shape (and make it rounder)?

Thanks,

Samir

[Samir Shah]

No one with this experience?

We found this guide.  http://www.revzilla.com/arai-helmet-shape-guide

We went to a motorbike store and tried on a Vector-2, and an RX-Q.

The RX-Q is their roundest bike helmet, and it fit my son much better than the Vector-2, which rubbed on the sides. The Vector-2 is likely to fit like the US spec GP6. So we managed to verify that a rounder helmet shape would be better for us.

I ordered the Japanese spec Gp6s.

Samir

 

[Samir Shah]

Watch out for the nose scraping. Fixing that was key to finding the speed. Also move the seat as far back as possible.

[Samir Shah]

I decided to get EMQ bearings – Electrical Motor Quality, made with 52100 chrome steel bearings. Slightly less Rockwell hardness than ceramic, but should be more than good enough. Also tight specs for play.

http://www.bocabearings.com/bearing-inventory/Electric-Motor-Quality-EMQ-Bearings/13722/10x26x8-MR60002RSC3EMQ

 

Samir.

 

[Samir Shah]

Hi Dan. Thanks. And thanks for asking.

We finally (and I mean just this past weekend) have the ikart working well- my son had some very fast times at Englishtown this past weekend. He had the fastest lap in the pre-final till he had a racing incident on his way to the front, and had this front bumper fly off – it broke and separated from its support when it hooked into another kart’s rear bumper in a turn .

We’ve been having conversations with John Martin to get it working, and also took it to Indy/New Castle a few weeks ago. John Martin has been pointing out some basic settings that we had totally wrong, which I have since corrected – switching to long wheel base, lowering the seat, moving the seat back, removing rear shims, moving weights to top of back of seat, moving battery behind radiator, etc.

 

I’m discovering that it’s a very tunable chassis – both my 13yr old and I are learning a lot as we experiment with settings and he develops the language and understanding to give meaningful feedback so I can make adjustments.

Also, we recently discovered that with the chassis being low, chassis protectors create understeer, as does the front bumper which wears out on the bottom rear. We removed the chassis protectors, and figured out a way this past Sunday  to raise the KG EVO front bumper (rubber hose on the bottom tube), and that seems to have made the kart work brilliantly all of a sudden, allowing my son to push with confidence as he now has front grip. (iKart has switched to a different bumper and fairing on their new karts, I suspect to fix this problem).

We’ve also always sucked at OVRP with this chassis and Rotax, with massive understeer problems, and I’ll bet it was due to the front bumper and chassis protectors. I need to take it back to try again now.

All summer, I’ve been pushing my son to find and explore the limits of the chassis – ie skid under braking in practice, go a little sideways, trail brake etc, which he was scared to do, given that it’s his first year with a 27hp engine, and the chassis understeered.

Once the chassis was balanced by eliminating the front bottoming out issues, he suddenly found speed! (A gear change helped too.)  To understand how much of a difference the bumper height made, Raif did a 41.575 sec in quali (5th) with the rubbing front bumper vs 40.885 pole; Raif: 40.719 secs in first race (pre-final) with raised bumper after our kludge rubber hose fix – which was the fastest lap of the event in all classes for both days till that point, till he got knocked out!

And all this with a sloppy front end as both spindles rock due to broken kingpin bearings.

 

I’ve still not gotten him to lock up or go sideways under braking, so I think there is still more speed to be found. And he still needs to learn to pass more aggressively, instead of getting stuck following the driver in front.

So, we’re finally liking the chassis, and I’m learning how think about kart physics and how to adjust it.  The last 2 races this Sunday were very exciting and gratifying for me, even though I screwed up by giving him the wrong gear for the final.

Stefano needs to try this chassis now!

Samir

[Samir Shah]

Another related question: rubber seals, or metal?

Thanks, Samir.

[Samir Shah]

Hi. Is the a full size chassis? RY30?

[Samir Shah]

So, have you looked at gearing? If its set up for road racing instead of sprint racing, it might not have torque and might be too long. Also, check the axle, bearings, etc. It is binding? Can it spin freely? Is the brake rubbing or stuck? Is the drive sprocket attached to the axle, or is the keyway broken, allowing the sprocket to spin without moving the axle.

[Samir Shah]

OK, based on this conversation, I ordered skid plates for my son’s iKart. Thanks.

[Samir Shah]

Thanks guys. Very interesting. So flat spotting at least is a no go.

Would it make a difference as to what age and size the previous driver was? A junior 13-15 yr old would race at 320-340 (larger kids) lbs, with much of the weight on the back of the seat, whereas a senior driver might be getting into 380lbs.  Or is it just bashing and griding?

Samir

[Samir Shah]

On my Leopard, I found that if I ran it rich, and fouled the plug, on the next session I could not rev over 7000-8000. Cleaning the plug with brake cleaner and a wire brush usually fixes it.

Reading through old messages, on the Rotax, if its too rich, there is also a 12k limit that some people have hit, and fixed by using a smaller jet that allowed them to get to 13-14k.

So, as people have suggested, the problem is certainly jetting, possible compounded by a fouled plug.

Samir.

[Samir Shah]

I’ve not been able to find a way to order one. Does your friend still have his extra’s – would he sell one?

[Samir Shah]

Yes, they came with instructions. Not the clearest pictures and pretty cryptic instructions (at least to someone that knew nothing about Rotax), but in conjunction with looking at an actual kart at the track I managed to figure it out.

Samir

[Samir Shah]

Does this software directly support the Rotax EVO upgrades? Or does one need to kludge it in? Which version is needed for EVO Jr Max?

 

Samir

[Samir Shah]

My understanding is that a worn chain will wear out your gears and sprockets to make it match the stretched chain. (they will look like waves instead of inverted Vs. Then when you put a new chain on, that chain will skip and not fit, and it will mess up that chain, and might cause it to fall off or break.

Samir.

[Samir Shah]

Check your spark plug. Is it way rich? Did you change to a much leaner jet? I am learning that the JR EVO jet is 115-125  vs 150-160 for the PREVO JR jet.

[Samir Shah]

FYI, all – the EVO Jr carb comes with a 130 jet and the needle at the 2nd position from the top.

I assume the 2 pins on the floats both need to be below the lever. One of them was above the lever on mine.

I made a throttle cable by grinding narrower (with a Dremel) the head of a Shimano bike shift cable!

[Samir Shah]

OK, got my lettered JR cylinder rotax engine! Got to convert it to EVO tomorrow and install it and get the kart ready for transportation on Friday.

I am hearing that the EVO jetting is different from the jetting for the PREVO. Any suggestions for JR EVO jetting and gearing for OVRP? Saturday is scattered T-storms, similar to the last time when we rented a Rotax JR. The jetting we used on the PREVO that time was 152.

Thanks, Samir.

 

[Samir Shah]

Solved! (I think).

There were 2 wires that were frayed, 1 was broken, they were also touching each other.

These were the 2 small red wires that are also attached to the larger red wire that goes to the + battery terminal. The broken one was responsible for the intermittent starter problems as well. Once repaired, the engine revved to 10+k rpm in my short test on the stand.

I let them sag and they rubbed against the ground!

Thanks for the input and thoughts.

Samir.

[Samir Shah]

How about the round thing inside the stator – I forget the name. Does that fail?

Samir.

[Samir Shah]

Hi Jim. Yes, I have an inline filter. I just rebuilt the carb, and I checked that the carb was clean under the blue cap. I’ll take it apart and check the popoff again.

Another thing that happened at the same time is that the onboard starter also quit at the same time. So wondering if it is a wiring or ground issue. I did check, and they seemed OK, but I will take a closer look once I get the kart out of the truck – it’s buried under all the stuff (we load it into an Expedition, and then fill up around and on top).

Thanks, Samir.

[Samir Shah]

I am going to swap the engines and see if that does the trick first. If it still does not work, then the problem is the electronics. Otherwise the problem is with whatever is bolted to the engine. Maybe the carb?

Samir

[Samir Shah]

What is involved in swapping out a numbered cylinder for a lettered cylinder on a JR motor? Does the engine seal get broken in the process? Can this be done at home, or does it require special tools, or is it required that a Rotax center perform this swap?

Thanks, Samir.

[Samir Shah]

Question about mounting weights on the seat for a Junior driver – should I mount the weights high on the back of the seat for increased jacking effect from leaning? Or low on the back or under the seat to keep the CG low and plant the kart? (The seat is already a little higher than an adult seat, to allow for visibility above the nose fairing.)
Thanks, Samir

[Samir Shah]

Hi. So today I’ll be pulling the trigger on buying one of 5 used/rebuilt Rotax Jr. Engines I’ve identified. I’ve also lined up an Jr EVO kit and will be installing that. The goal is to get the engine during the coming week, and be ready to race at the NE Regional at OVRP next Sat and Sun.

What other Rotax parts and tools will I need? Here are some that I’ve identified. Anything else?

– Battery: can I use an equivalent battery, or do I need to use the spec -Yuasa or Rotax branded batteries?

– Is there a spec oil for Rotax? Or can I use the Motul 2T I have for my Leopard?

– Mojo D1s

– Engine sprocket locker thing to lock the flywheel and allow the clutch drum and front sprocket to come off?

– Exhaust springs – they need to be Rotax?

– Rules specify a rear tire protection system? What is this?

” ROTAX rear tire protection system is mandatory to be used. Either 2-tube version or 3-tube version, third tube might be mounted above or below the two main tubes. No part shall be added or removed from original content (except safety wire or bolt connection between pos. 1 and pos. 2 as well as number plate with support). Only orange or red ROTAX original tyre-protection rollers are allowed to be used.”

Would appreciate and tips and knowledge about tools and setup issues and things to watch out for. Thanks, Samir.

 

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