998 vs. 990

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Dreggsta

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I don't have any scientific evidence but i drive by feel & can say that to me the 998 has a bit more throttle snap than the 990. I did add some taller than stock xt tires although they are lighter & thinner. The 990 is a great carb. I guess it's like the 990 but w/more throttle snap. Is it worth it to get it? I think so. But I'm ocd bout my set ups lol.


I did shoe goo the throttle shaft hole too. Actually before installation.
 
Dreggsta said:
I don't have any scientific evidence but i drive by feel & can say that to me the 998 has a bit more throttle snap than the 990. I did add some taller than stock xt tires although they are lighter & thinner. The 990 is a great carb. I guess it's like the 990 but w/more throttle snap. Is it worth it to get it? I think so. But I'm ocd bout my set ups lol.I did shoe goo the throttle shaft hole too. Actually before installation.
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I did a comparison of the 990 and 998 today because I was second guessing my self..I'm glad I did, it reasured me the 998 was a better performer. No flat spots and a definate power increase when you hit the throttle, it was something I could see, that makes me a believer.. Awesome Carb, good choice!
 
Hey man, I wanted the 813 but shyed away from it bc of the throttle shaft issue. Then you come along talking bout this here 998. I gave in bc of you lol & bc it was what I originally wanted. Pretty cheap mod too. I gave my 990 to my son's xt-b so win-win! Lol. Thanks for posting the info you did & not keeping the info to yourself.
 
hey meat, you have any issues w/your 998 sticking at a high idle & stalling out? Mine acts like it sticks at a high idle & then frees itself. Also it stalls out periodically. Full tank if gas & tank is vented well. It didn't do this at all last night. I'm not to worried bout it. I'll get it straightened out. Just looking for ideas til I can get to it.
 
Nope, no issues. Make sure your throttle linkage has a little slack and there is no binding when at idle. Also, idle surge can be a vacuum leak or possibly a blockage of some sort. I like to raise my idle and fine tune the low speed screw, once set I drop down the idle. Be sure not to lean it out to much, this kills power at low end and can cause stumbling. If you still have issues, reinstall the Carb with proper tightening sequences to avoid warpage. I also double up my gaskets for more squish and better sealing as a fail safe. Take two gaskets and put a very fine amount of sealer between them, enough to just coat them and the place them together, wipe off excess and re assemble. This works great for me and its a cheap trick.
 
Dreggsta said:
Hey man, I wanted the 813 but shyed away from it bc of the throttle shaft issue. Then you come along talking bout this here 998. I gave in bc of you lol & bc it was what I originally wanted. Pretty cheap mod too. I gave my 990 to my son's xt-b so win-win! Lol. Thanks for posting the info you did & not keeping the info to yourself.
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I think the shaft issue is fixed, also, I did not plug that port as I did not see a need to. The Carb works awesome as it is set up. Just bolted it on, tuned and ripped!
 
Dreggsta said:
hey meat, you have any issues w/your 998 sticking at a high idle & stalling out? Mine acts like it sticks at a high idle & then frees itself. Also it stalls out periodically. Full tank if gas & tank is vented well. It didn't do this at all last night. I'm not to worried bout it. I'll get it straightened out. Just looking for ideas til I can get to it.
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Haha, I had the fuel lines reversed and it did as you explained. Would idle then fall on its face lol. Stalling is usually a rich issue at idle. Finding a good AFR is key before dropping idle down. Be sure to set idle high enough so that if you come off full throttle under load it does not stall.
 
I want to try the 813 or 998 but I can't find the 998 anywhere but ebay and I refuse to order anything off ebay (too many bad experiences) and the 813 is out of stock :(
 
I'm bringing in some of the 998s to try. Will have them in a couple of weeks if you can wait that long.
 
RCDAD said:
I'm bringing in some of the 998s to try. Will have them in a couple of weeks if you can wait that long.
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Yeah I have waited over a month for my other 990 which still won't be here until June so what's another few weeks plus your prices are always reasonable and service is just top notch and I get to support the forums, so yeah just shoot me a price so I can add it into my budget for my next purchase of parts. :)
 
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