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Removing the XR200R choke plate ok?

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I looked on the internet and only found 1 reference to doing it; and that was when using the XR carb on a smaller hopped up pit bike ..

 

Can the plate screws be removed without their staked ends damaging the threads on their way out?  Maybe grind the staked partd off before you put a screwdriver on them?

 

By removing that choke and its wing effect do you lose low end? Anything negative about taking it out?  I started my engine easily by just squeezing the air box to carb booy shut, hit the starter button, and it fired right up without hesitation.

 

Sounds like a winner   :ride:

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Never tried running without the choke plate.  What is interesting about the choke plate is when in "run" position it sure looks like the the aftermarket "air wing" things that control air flow and improve throttle response. 

 

Yes it does look like the Scary Fast and other home made inlet devices claiming to aid performance. Though a bit thicker and then there's the shaft running across the bell.

 

The idea for removing it is to gain unobstructed flow/cfm.  I'm living in the Philippines, and the weather never gets below maybe 70F so a choke isn't really needed.

 

I had an extra intake manifold from eBay, so I tried something I'd been wanting to do by adding a divider made from  a section of pocket rule to it. I managed to get a straight cut with a 32T hacksaw blade and the JBWeld is holding up fine.

 

I am still waiting on richer main jets to arrive, but testing this device briefly definitely showed something different going on. Possibly more low end torque at the expense of high rpm, because it wasn't revving as freely, but - going thru the gears in my usual testing section of road still showed nice torque-y acceleration. Just not revving as high. I'll have to compare acceleration mph between points A and B and see which  is actually faster once the jets arrive. (maybe this week)

 

My gearing is 13/48..   

 

Anyway, if this modded intake has affected power in a negative way, then of course the choke plate stands a good chance of doing the same,  I really couldn't find text or images of people removing their choke, which you'd think would pop up now and then since having that choke plate in there isn't something found on all carbs, and it'd seem a natural to take out.

 

Once  my jets arrive I'll investigate the intake and maybe removing the choke some more.  This informative spark plug article points at my jetting being lean so not much sense it hammering it right now

 

Interesting that  this and other articles point at the air/fuel ring at the base of the spark plug as the first place where to identify rich or lean, with the porcelain being second

intakemod.jpg

Edited by ViperGTS

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Or maybe it was rich..  :jawdrop:

 

Trying the test method of WOT for a few seconds, then back off to 7/8 throttle found the bike hesitating ...so I backed off from a 128 main jet to a 122 after trying the 125 and getting a similar but smaller hesitation. 

 

 

The test is started with the engine running at an rpm high enough to ensure that it is “on the cam".

Open the throttle fully and let the engine pull for several seconds.

Then, quickly close the throttle to about the 7/8ths position.

If the engine seems to gain power, the main jet is too small (lean). Fit a larger jet.

If the engine hesitates as the throttle is rolled off, the main jet is too large. Fit a smaller one.

When the main jet is correct, the engine will continue to run smoothly and evenly as the throttle is closed.

 

I'm going to try pulling out the choke and capping off the left side with a vacuum cap-assuming the plate is what holds it all in and its not a big deal to put in or out

Edited by ViperGTS

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- I took the choke out.  That's a lot of junk obstructing the carb and i'm sure it being gone has gotta add a few cfm of flow. I didn't notice any loss of low end, so maybe the ScaryFast effect wasn't happening anyway

 

First though, I ground the end of the ends choke plate screws the 1mm or so down to the level of the shaft with a Dremel because they're staked/spread out at the end and will sometimes de-thread the holes as you take them out.  :facepalm:

 

 

Technically I suppose removing the choke plate and shaft calls for checking the jetting but with my  a/f meter and exhaust bungs due here in a few weeks, I'll probably just wait for it.  Unless I can find another bike to race against and do some before/after roll-ons

 

Though now there's the question of the modded intake with the choke out and proper jetting haha

 

Still anticipating getting the Webcam in ...

 

time just slips away

Edited by ViperGTS

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Well I couldn't wait and installed the modified intake. Predictably it was richer with that intake on it (more vacuum over the main jet?)- slightly failing the roll off the throttle at WOT test by hesitating a bit when I did. 

 
So I backed off the main jet from 122 to 120, and it seems to be revving good with the mod intake -  better than when the choke was still in it, without hesitating when I back off WOT a bit. Removing the choke must have helped.  If the intake mod has created more velocity it'd stand to reason that the jetting might have to be leaner..
 
That about does it for me now on the choke/modified intake issue I guess
 
 
:ride:
Edited by ViperGTS

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Before and after; which one's going to flow more air?

That would all depend on the size of the valves, the lift and duration of the camshaft, and the overall design of the head {intake/exhaust passages}.

Should be a bear to start in cold weather though! LOL.

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My testing the other day seemed to show increased performance over my usual test section of nearby highway, gaining 1-2 k/ph in a short sprint.   It's easy enough to try if you have a good testing  plan, and put it back in if your engine doesn't respond to the change

 

 

It's never below 75F here-if even that low

 

For those who have to contend with cooler temps just put the choke back in when it's not Summer. I just squeeze the air box boot first start in the morning to block air flow and give it a little choke effect. Then I'm good for the day

 

There are ways to get around the cold start issue if you want the added power bad enough. Some performance carbs (FCR?) have no choke system at all

Edited by ViperGTS

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I added the.300 lift / 282 duration Webcam this week.  Just last week while doing the intake mod testing I couldn't go over a 120 main jet. Now a 125 seems just right  while doing the roll off at WOT testing. Not a hint of richness. (128 tested rich today)

 

Also added a 45 pilot replacing the 42 before testing main jet today and no sign of richness with the 125/45 combo. The 42 pilot may have been too lean already, but the bottom line is this cam needs more fuel AND seems to rev higher and easier

 

I'll double check the 125mj then add a 48pj this week end

 

:thumbsup:

Edited by ViperGTS

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I video'd some runs today using intake manifolds with and w/o the divider (choke plate in place); then came back and timed the vids over and over.  Either way after the standing start, the time from 20-80kph was just a few hundredths different between the two, and the kph in the vids at the finish line appeared to be the identical.   :bonk:

 

Although.. the knobby spun on the pavement during the 1-2 shift and a little on the 2-3 shift when speed shifting at WOT with the divided intake; with the stock intake it did not.  Tire spin would slow the ET some, but not the KPH trap speed I suppose..

 

I'll have to rig up a stopwatch to the RH mirror stalk triggered by an L-shaped piece of Al clamped to the throttle to trigger the On/Off button like I use on the KLX to get more precise timing before I bother taking the choke plate out  to compare power with it and without.  That choke plate and rod is a pretty big obstruction in there IMHO.

 

 

Even in this tropical weather with mornings in at least the high 70s, starting without the choke is a pia; but I am curious about how it'll run without it-and it's something to fiddle with

 

 

:)

Edited by ViperGTS

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