Okay guys, I'm bored as hell (look at the time this is posted at ) and I have something that is bugging me...

I have an 85 Honda 250R... runs really strong, pulls tremandously hard, idles great but the throttle is very touchy and there is hesitation at full throttle in any gear. If you take off and can keep it in it's "sweet spot" it's a little rocket until the throttle is maxed out... then it just sputters.

Again, I'm no bike mechanic but I'm thinking it's the jetting. Here's the history on it...

It was bought stock from the original owner by my best friends dad (Chevrolet Master Technician) in the early 90's. He took it out to Glamis on a few trips with us and never had a problem with it. One day, got a hair up his ass, decided to bore it out a bit (Wiseco piston), throw a CR125 carb on there (does this make sense? I was thinking CR250 if anything), thinner CR head gasket and some porting. He took it out for a trip, noticed it was ridiculously fast now, couldn't keep the front end down and came home and custom made a +6" swingarm to control it more. He took it out a couple times after that and soon lost interest in going to the dunes. I begged for years to buy it, then one day he sold it to me.

I took it out for a few trips after I bought it, proceeded to whoop the crap out of my brother on his 250, then one Saturday I noticed it was leaking at the base of the head. I took it to my bike mechanic (the guys a genius and charges almost nothing for labor... beyond cool) and he took a look at it. Turns out the porting was crap, had to replace the gasket and he decided to bore it over a tiny bit again. He freshened the whole thing up, I spent a whole day breaking it in... slowly... and we then rode the rest of the weekend it was faster than before... . However... it still had the issue with the top end. I run 32:1 on the fuel mixture with 50/50 91 and 110.

What size jet(s) do you guys think I should run in this thing considering the higher compression and whatnot? Does the CR125 carb make sense? I'm thinking it doesn't but, the thing is a rocket regardless.

Thanks.

(It's amazing what I can think up sitting for a month with nothing to do ... I can bend my knee 90 degrees now though )

Well the first thing I would do is change that carb out to a 38mm keihin PWK and run a 190 main with a 62 pilot.

If you have a inline fuel filter get a new one.

I assume you are running a K&N air filter if not get one.

That should take care of your problem...

It sounds like that carb is not giving you the mixture your bike requires to keep on the top end and if that is so you stand a good chance of running lean and burning a hole in the top of your piston. What I have suggested above should help allot and with that setup run a 40:1 or 50:1 gas/ oil mix with 50/50 92 octane and C-12...

Carb is too small.
Get a 38mm.

Check your reeds too.
A small crack usually becomes noticeable at high revs.

Thanks guys... that's pretty much what I was thinking.

When he told me about the carb, I just got that "Huh?" look on my face but never looked into it.

I know the reeds got replaced last time around... David made sure that happened.

I ordered a K&N for it from ECC a while ago... they called and said they had it in, went to pick it up and it was a stock filter... now I'm waiting for the K&N again.

Mr. Dune...

Thanks for the advice on the jets... gonna look into a new carb and see what happens.

I'm having this same problem right now with my 86, the motor is pretty much stock with the exception of a cr head gasket and pipe, the carb is stock and I cant remeber what jet is in it but I will find out tonight, the air cleaner is a white brothers in the stock air box. When you guys run the K&N are you still running the air box?

You can either take the lid off or drill holes in it to open up the box more...

I remember seeing a post in here for a company that makes covers for air boxes... same size as air box cover just with a screen in it.

Save your money and get a Outerwear for the K&N instead of the screen replacement cover. Remove the lid to let the air in that's what I did before I got rid of my airbox...

i run ESR's airbox eliminator and i love it. gotta cut off one of the air box mounts but i dont care. i can weld that back on later if i want it back.

im going to say main jetting is wrong.

I would say the main jet also(go up one) and I run mine with the lid off with a K&N and outer wear

Ok here's what I got. Stock air box with top cut out then wraped with a panty hose. my main jet right now is a 148 and the pilot is stock, I have a Paul Turner pipe with a Answer sparky and the CR head gasket, nothing else has been done to this bike. I have always ran the bike with a 50/50 mix of race gas and 91. So what do you guys think?

I does sound like jetting, but if you've been running it for long like that and your spending time changing the carb and stuff, buy a head gasket and pull the head off and check out the top of the piston, just to make sure there's not a hole waitin to bust out. Every time that happend to me, top end sputter, it was always the piston.....FYI.

Thanks for the info guys, I'm going to try a few bigger jets this weekend and I'll let you know what happens. I use any where from a 40:1 to a 50:1 mix it all depends on how many of these I've had when I mix

Toy Collector, Sorry for Hi jacking your thread but it sounds like you have the same problem I have right now, so I hope the info in here has helped you.

do a plug chop and refer to this guide

http://www.eric-gorr.com/techarticles/sparkplugs.html

Anyone know the best place to get a 38mm Keihin PWK?

www.esr250.com or www.ctracing.com

make sure u get that cable, ESR air box eliminator, and a cr intake.

BTW, i just ran mine for the first time this weekend with a 170 main. ran like a dream and im damn happy with it on a 250. i cant wait to try it on a 295.

Update:

Took the bike apart a bit today and found out it has a 37mm carb.

Looks like I'll be ordering a 38mm in a few weeks.

a stocker is like 34 i think.

my 38mm air stryker will be for sale in the coming months and has barely tasted 5 good trips worth of gas.

going bigger.

HA2,

Let me know when you are ready to sell that 38mm A/S.
I may buy it from you.

you got it. either way, she'll be in the for sale forums unless we hook up first.