Seat Choice and Mounting for Tall Upper Body in LO206 Sr

2009 Monza (Blue Birel) R30CY
30mm main tubing, no front or rear bars
40mm Freeline “F” Axle (Fairly soft), no middle bearing
LO206 Sr (365#) at Whiteland Raceway Park (Whiteland, IN)
4.50"(on 5" wheel)/7.10"(on 7.75" wheel)Bridgestone YLC (Required Rubber)

I’m 5’10" and about 175 lbs, but with a 6’2"+ equivalent tall upper body (my inseam is 28"), the current seat is an IMAF F6 in ML and is super haggard and needs replaced. Looking for a sounding board type feedback/recommendation for my situation or all taller upper bodies in general

Last season (my first, only have 5 races under my belt!) I was having some intermittent issues with the kart binding and hopping through hair pins (mainly the rear). Some friends at the track said I was wayyy too wide on the rear and upon listening I went ahead in the offseason and switched to narrower rear hubs to try and free it up. (Went from about 115 mm to 100 mm hubs each side)

The problem I have is the track has went through a pretty substantial and much needed repaving in the critical turns. And since the old “medium to low grip” track was giving me a hard time, I will probably need to shift my setup window a bit to help free the kart up. I.E. try and soften the rear with the new seat.

So when picking a seat I was eyeballing the Tillett T11 VG (flat bottom and soft), and was planning to mount it per the setup guide from Birel I found for Tillet seats (10 mm below the frame rail).

Am I crazy or does this seem fair? Should I consider mounting the seat a little different? Flat bottom with ground clearance doesn’t afford me any flexibility in terms of angle (all tilting options will cause a higher CG than parallel with the ground). Still have plenty of ballast to throw around (was about 20 lbs), and a few other hub options for further tuning.

This year we will run a 30mm 2 cycle chassis in 206 and a T11VG with a 6 ft tall driver 4mm below flush. Last year we ran the same but with T11 standard Seat flush w bottom. It took us a good part of the year to get everything right including 206 driving style as our experience was always 2 cycle and this was new for us. However, by the end of the year we were usually one of the fastest karts in terms of raw speed. We had a few front row starts in CIK at new castle, had a pole or two, and had a few decent runs at Whiteland.

So… I’d say you are for sure on the right track in my opinion, especially at your weight and torso geometry. I’d make sure you have the softest axle you can find. Ride height low as it will go. My last piece of opinion… since you have a two cycle chassis, set it up like a 2 cycle chassis. We tried to do all the crazy narrow stuff like the AM29 or Eagle or MGM… and it absolutely did not work for us. We reset like we were running Yamaha and it started working really well.

We have a 50mm axle and 25mm front spindles but will be running 17mm spindles this year along w the VG but plan on keeping the super soft 50 mm axle. When we get a hop like what you are speaking of it’s caused by either transferring too much to the outside rear and digging in the sidewall or it’s more or less laying too flat and binding. I don’t know where you set your caster and if you have seat struts etc but make changes both directions and see what works.

Based on what you said, I’d bet getting the rear at a normal width for that chassis (shorter hubs are still good) and normal to 5mm wider than standard width in the front will help. Ballast weight towards the front could also help a bunch. This is just one guys opinion, some will disagree with me…but one thing everyone will agree… make changes In all directions and see what happens!!

As far as your question about seat mounting… my opinion is mount it EXACTLY where Birel says to mount it. Remember that this seat may have slightly different dimensions than a freeline seat so be sure whatever measurements they provide is cross checked with the seat differences. I would bet that PSL or someone would even have the perfect dimensions translated already to a T11 if needed. I know almost nothing about Birel but I know OTK dimensions were to the front of the seat which could be different for different brand seats.

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What 2 stroke chassis are you using?


Here are some miscellaneous thoughts I have pertaining to your situation. These are based on my experience tuning for a taller driver, my brother- 6’3", in the past, as well as a few years experience with a similar generation ('08-'11) of Birel karts as what you have.

  • Keep in mind that many newer 4-cycle karts are designed completely differently than the kart you have. I’d advise against taking specific setup cues from those drivers/karts, as the results may be different with your equipment. I would instead recommend testing in order to find what works best.

  • Most of the Birel factory seat recommendations are based on tires/classes/circuits in Europe instead of what we see here in the states, and 10mm below the frame rails has always been the baseline within those setups. Generally running the seat this far below can create issues with scraping, and unless you’re fond of fiberglass repairs, I would instead proceed with the seat 0-5mm below from frame. I’ve found that leaning the seat back in order to lower the driver’s head position achieves a similar outcome in terms of handling implications.

  • I’d recommend starting with a standard Tillett T11, or possibly T11t. We didn’t often use the VG on the older Birel stuff, and I think going that route would be too soft. As mentioned above, lean the seat back as needed to lower your head position. This can be tricky with the flat-bottom seat, but I believe it’s necessary for drivers with more upper body weight.

  • Here are some old notes from the Birel factory team regarding (what should be) the exact frame you have. Probably best to use this as a baseline and then tune from there. They mention a 6.0 rear tires, as I believe this kart was commonly used for a Junior application, but this should still get you in the ballpark.

What I take away from these notes, in conjunction with your feedback:

  • You’re likely set up a bit too soft
  • You’re likely set up a bit too narrow. Definitely double check your final rear width vs the 23cm hub setting mentioned above. Depending on the wheels you’re running, this may put you close to max width, which is probably too wide. Might be best to start around 54" total rear width, and go from there.

Lastly, I was just out at Whiteland on Saturday, and got to walk the track and see the new surface the just put in place. The difference in smoothness is going to be night and day vs. the old surface, especially in the inner hairpin where you mention your handling issues being most pronounced. Moral of the story here is that your best source of information will be testing, testing, testing! Best of luck, and hope this is helpful.


This is spot on advice! Every chassis is different but based on my experience with Birel you want to stiffen things up when your kart gets tight and the track gets grippy.

I’m 6’1", 205lbs and I ran an RY30 with a Tillett T11t last year. After trying everything under the sun to get the kart to stop 2 wheeling around high and low speed corners during the summer last year… The biggest change came when I rocked the seat back to lower the COG and stiffened up my rear axle. Also, try reducing your track width up front. Take some bite out of the front to make the kart turn in and rotate slightly more gradual.

Depending on how experienced you are, you can start to play with caster etc. But lowering the COG by rocking the seat back and changing your axle will by far be the best bet.

I have changed my seat again to a Tillett T9.5t this year as it is specifically made for drivers over 6’0". You can go that route for your seat choice, or grab a regular T11t and rock it back a bit. I would stay away from the soft Tillett seat if you plan on running the Birel. PSL pointed me in the direction of the T11t and it seems to be the best fit for the Briggs.

I hope this helps.


Thanks all!

I’m blown away by the quality and depth of the responses, here. Way different than my usual experience on other forums. :slightly_smiling_face:

Thanks for steering me away from the VG, and righting my mindset in general. I’ll be going up to Comet on Thursday to get some bits and should be able to get my size sorted with my rib protector on.

I was able to locate that setup guide before (pretty darn close to what I have), I guess I wasn’t sure how to counter the fact I don’t have a front bar or a middle bearing. Softer on both ends. My brain is still very much new to karting/used to suspended car tuning.

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I don’t know about you, but my hopping in the hairpins were not from binding up. I was free as a bird all year and hopping all over the place after the patching started to come up. It was the surface mostly.

If you’re at Comet, ask Rex or Steve to see a Beasley and ask them what they think about putting it in your specific kart.

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I had an ry30 a few years ago and started experiencing the same thing. I’m 6’1" and 210 do I fight this issue a lot. Running it out to full width helped. A lot of the newer chassis for 206 are designed to run pretty narrow on the rear axle. Try decreasing the castor and narrowing the front track too. Contacting PSL or Austin at QG3 for Birel questions. Both are a wealth of knowledge. I will agree with @CrocIndy on the Beasley seat. They help bring that cog down for taller drivers while still being a CIK legal seat.


If you can’t track down an OEM front bar, any other 30mm bar would do fine, and just cut it down as needed.

The third bearing may be a little trickier, but you could try calling around, and keep an eye on Ebay listings and such.


If you need any help at the track, I can stop by Whiteland or New Castle and help out sometime depending on the day.

Energy Space …

Update: I went ahead and installed a T11t in the Birel specified front/rear position, and laid it back - bottom 5mm below the chassis, to the min rear height I saw for all the relevant rulebooks I could find (WKA/CKNA/SIRA).

Went ahead and did some testing a few weeks/days ago at baseline specs and started at proper Sr. weight and 42.5% front, 49% cross.

Wow, this made a YUGE difference! At the baseline with the seat in it’s new position, the kart felt like it was working alot better, and the front end felt really solid with the front bar.

At the end of my testing I ended up removing the 3rd bearing, removed 1 half spacer up front, and narrowed the rear up half an inch from 54.5" to about 54". Anything more on the rear and the front started pushing. But holy crap this thing feels like a newer kart. Thanks y’all for some bang-on advice.

Now I just need to drive faster :slight_smile: focused on un-learning my Camaro habits.

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Thanks for coming back to report the outcome.

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