Big Bore 350 problems!!!!!!!!!

[jon370r]

Has anyone ever had trouble tuning their bog bore engine? I've been around 250R's for a long time and have always done all my own work, but this problem has got me stumped. It first ran like it was rich and would just bog on top end now it runs like it has a rev limiter ( bah,bah,bah,bah sound).This was a complete engine rebuild a new 350 PV cylinder. Did a leak down test after assembly and it checked out great. The engine has 175 lbs compression. I have changed every electrical component even though the ones on the Quad all tested good. I have tried 3 different carbs(38 PJ, 38 Airstrikeand 39 PWK) with main jets from 175 to 200 and every different size needle I had. Tried Boysen Radvalve and VForce reeds and the problem won't go away. I have tried every 250R trick I know and after 2 months of fighting with this is really pissing me off. By the way before I put this motor in I had my spare motor with a regular 250 cylinder with all the same electrical and carb components and it ran fine, would rev to the moon.

[dober250R]

keep going up on your main jet until you foul a plug. My guess is you're still 2 lean..........

[jon370r]

I ran with the 200 main in it today and it didn't run any different than when I had a 178 in it 2 weeks ago. The main should be somewhere btween 180-190, thats where I have always ended up on the jetting in prior years and prior rebuilds depending on temp and conditions.

[zedicus00]

whas yur pilot jet? what type and clip needle? and i think it does sound like yur just lean, my 310 resleeve jug is runnin a 200 main jet. also a 350 is not gunna over rev anywhere near like the stock 250 setup will. with the 39pwk try like a 60 sumthing pilot, DGH needle middle clip or richer and i would start with a 220 main and be ready to go richer with it too...

i dunno i could be way off but u said u did a leak down and tested all the electronics, got a good plug with a correct gap?

[Aceman]

Have you made sure you have a clean ground to the engine?? Seems like I remember reading a long time ago a guy had a problem revving his motor past a certain rpm because of a bad ground. Just talking out loud here.....:confused:

[86trx250R]

i had a similiar problem on my 310...gap the plug to .18 see if that works....

[fireburns99]

i also think you should try gapping your plug smaller. Maybe .020-.018. I've had good luck when i've done this.

[dober250R]

my 250R was sounding like this when i rode at the dunes ( the rev limiter sound) will making the gap smaller help this?

[Eddiesanders250]

Bee i think he needs your help.............

[C-LEIGH RACING]

Its probably more than likely the ignition system causing the problem.
After changing that many jet sizes & other things on the carb & it didnt solve the problem, check or replace the ignition system.
Heres a tip, in your wiring harness, up at the CDIbox, the black wire with the white stripe is your main ignition wire.
Sometimes that wire end connector can have a bad connection & cause the engine to run just like how your saying yours is running.

A CR250R replacement ignition system is the best favor you can do for yourself on the 250R. Check with Eddie Sanders Racing, he has all the parts you need to replace the old system comes in a kit form & at a good price to boot.
Neil

[jon370r]

Trust me, like I said I have tried every 250r trick in my book.

1. different plugs (everything fromb9ev to br7es) gaped at anywhere from .015 -.030

2. Complete wiring change(harness, CDI,coil and stator)which were all like new from my great running red 250r.

3. I ran a grounding wire directly to the head even though the continuity tested fine from the plug to the frame just to eliminate that.

4. CEK,DGH, and other needles (I couldn't identify necause the markings were worn off) in every clip position.

I'm hoping someone comes up with an idea that I haven't thought of or tried yet.

[PYF]

Just subscribing to this thread just in case since my 250r did the same before I rebuild it and wonder if it will still do when It will be rebuild + a new coil

[robyone]

Loosing any coolant? Possibily an internal head gasket leak :confused:

[bada440ex]

one time my r had that bla bla bla sound on topend i found out that the spark plug had a peice nocked out of it yours could have a crack in it or something

[C-LEIGH RACING]

Yeah thats right, sometimes it can be the simplest things causing this.
You useing resistor plugs, if so try changing to a regular plug.
Neil

[jon370r]

Yesterday I tried a NGK and a stock CR plug cap. I ran it with B7ES and a BR9EV plugs both gaped at .018 and no change what so ever.

[86trx250R]

cant wait till you figure this out ...gonna be something simple...fuel filter.....how about your petcock...

[jon370r]

The fuel flows fine and I even just added a Boyesen Super bowl to the caeb for more capacity.

[BLACKeR]

your silencer isnt plugged up by any chance? no packing is loose and blocking the exhaust flow? thats pretty much the only extra stupid thing i can think of.

[jon370r]

I've tried both my silencers (FMF and ESR) and with no silencer at all. Tried with new clean airfilter and no airfilter, no change.

[C-LEIGH RACING]

Blacker, man I had forgot all about that silencer deal till now.
We had one come apart inside, the core broke loose & blocked the opening, we worked our tails off trying to figuare out what was wrong & in the end seized the engine.
While we were taking the engine apart, a kid walks up & was watching us & I seen him stick his finger in the pipe, I'm think that going to be a black finger for sure & then he says, your pipes messed up, WHAT, come on kid we got work to do here now, & then he says it again, so I look & sure enough the core was broke & blocking the outlet.
After that I thanked him & got the little guy to come to the front of the trailer & loaded him up with LA Sleeve, Pro-x , CT & ESR decals, he walked off a happy camper. I guess that just goes to show sometime in haste a feller can git kinda dumb at times.

I leared this much from that for sure, when you have an engine not running right & it did the day before & you think its the jets, if you got the change 3, 4, maybe 5 different jet sizes & the problems still there, you can rest assured its not the jets, unless its a fresh engine & you jetted WAY rich to start with breaking the engine in.
Neil

[novaracr70]

stuck power valve?

[jon370r]

I've had the powervalve out and seems to work fine. I even ran the motor with the powervalve end cap off so I could see it work under actual running conditions.

[rebelbanshee]

Originally posted by BLACKeR
your silencer isnt plugged up by any chance? no packing is loose and blocking the exhaust flow? thats pretty much the only extra stupid thing i can think of.

yeah...that really sucks. Neil you pretty much described my weekend minus the engine burning up.

What does the plug look like? that will tell you alot.

[matt250r21]

Is the little E clip on the needle? Mine wore out and the bike would run, but really bad. Check your carb slide just to be sure.

[jon370r]

I've had 3 diffetent cacbs on it in the last 3 weeks with needles set at all from max to min, main jets from 175-200 and float levels all checked. I have elininated the carb and the electrical from the potential problem. I need to get some ideas of that elese can cause a problem like this. I've gotten to the point I'm going to pull the 350 pv Topend off and put my 250 powervalve cylinder on and see how that runs. I plan on doing a Hot leak down test before pulling it because that is the last thing I can think of besides the actual port timing to check.

[dober250R]

please try a 225 main jet before u rip anything apart!!!

[Aceman]

If everything worked fine before the 350pv and now it doesn't run right and it sounds like you've checked every component, I'd just go ahead and swap the topend out. You need to eliminate every possible problem and the 350pv topend is one of them. Even if the 250 pv topend runs just as bad then you know it's not the cylinders with the problem. JMO though.

[matt250r21]

Any chance your pipe could be pluged up with a rag during rebuild? Not your silencer but the head pipe or exhaust flange.

[250r4life]

Originally posted by Aceman
If everything worked fine before the 350pv and now it doesn't run right and it sounds like you've checked every component, I'd just go ahead and swap the topend out. You need to eliminate every possible problem and the 350pv topend is one of them. Even if the 250 pv topend runs just as bad then you know it's not the cylinders with the problem. JMO though.

and waste the money he spend on the top end?

possibly if he was gunna send it back to CT, but i doubt they'd give him any money back... there has to be a logical explanation

[Aceman]

I'm saying try swapping the 350 jug for the 250 jug he has and see if the problem is still there. Nowhere did I say throw the 350 jug in the trash, can't figure out why you say it's wasting money unless you think gaskets are expensive?? :confused:

[spent21]

I agree with the previous post about plug chops. what does your plug look like? maybe you have a small air leak around the base gasket? i cringe to think that maybe the port timing may be off a smidge? the jug swap would narrow it down to a gasket or the jug itself.
just throwing ideas out there.

[250r4life]

Originally posted by Aceman
I'm saying try swapping the 350 jug for the 250 jug he has and see if the problem is still there. Nowhere did I say throw the 350 jug in the trash, can't figure out why you say it's wasting money unless you think gaskets are expensive?? :confused:

my bad... i shoulda read your post a little better... i was thinking you were saying just ditch the 350 and go back to the stocker... and essentially you were- for testing purposes... you're right, i agree...

[Meat]

jon, sounds like your rich on the mainjet. boggin\4strokin' on top means a too rich main.

[norcalduner]

i had a very similar problem on a 330r which i eventually sold and the person i sold it to eventually found the problem after several "swaptronics" attempts to be a bad cdi. just thought id throw this in. good luck jon.

p.s he originally swapped in a new cdi yet the prob still persist so he unwillingly bought a full esr ignition kit and bingo !

[hang1p]

jons going to borrow back his the 97 cr set-up from my bike and give it one last electrical shot before the tear down, alot of good ideas out there thanks for chimming in

[Aceman]

Have you figured out what the problem is??

[jon370r]

I spent 4-5 hours working no it last sunday with on luck. I thought I had a timing issue I worked on for awhile but that didn't prove out. Then I swaped the 350 cylinder onto my spare engine and instaled that. Ran the same way (like chit). The last step is to pull the 350 and put on the 250pv topend. I just haven't had the time or ambition to do it. After I pull the 350 cylinder I'm going to try to map the port timing to see where it is. I've never tried that, should be fun.

[skyhighatv]

same problem with a 330 non-pv
for pro-x cylinders ct calls for-
b8eg
b8ev
b8evx
just found that out-will be trying later -ill post back with any luck.

[custom R]

This probebly sounds funny but check the gas cap i had the same type of problem last weekend and after about an hour I loosend the cap and it ran fine turned out my vent hose got cloged so it would fill the bowl with gas but after i got up to speed it would starve the motor of gas

[250r4life]

lol... had a buddy with the same problem last summer... i had forgotten about that.. yah the vent tube got clogged and it would cut out like crazy...

[GOTFEAR]

Yea I had the same problem with my 350 i found that when you run a boyson radvalve and spacer the motor is wonting big gas and larger than you think jets and you need to run no smaller than a 40mm carb because with smaller one the motor wont reve out with the same sounds that yo have and had to close my adjustable lrd completly up on adjustment and after that big power Zzzzzooommmmmm............

[hang1p]

me and jon both have 350's and ride together he has a powervalve and i do not and I'm running a 38mm airstriker like him and mine runs fine good call on the gas line vent never thought of that one

[250r4life]

any updates? any time to work on it this last weekend?

it wasnt a clogged up vent tube was it?

[jon370r]

I swaped my 250PV cylinder onto the base in my quad today and changed absolutly nothing else, even used the same sparkplug out of the 350PV and it runs great. Revs clean and revs to the moon. So yes the problem appears to be with the cylinder itself. I had checked the powervalve function and even tried it without the spring so it would just stay open all the time (saw that on a Banshee website) so I would have to suspect some kind of port timing issue.

[spent21]

sorry to hear that. was it new? that was my worse case scenario, but was definitely a possibility. is it possible that the jug needs a spacer plate? i am not sure that they will even run if it needs one, but i've never tried.

[dober250R]

maybe it just needs a new set of rings? or the piston to wall clearance is out of whack? Just throwing ideas out there.

[jon370r]

It was all new when I assembled it. The engine was origionally planed on and built with a short rod needing no base spacer. I couldn't get that tuned correctly(ran like crap) and when I swaped to my spare engine base, that one is a long rod so a spacer was used and ran the same exact way. Both assemblies passed the leak down test with flying colors and had 170-175 lbs of compression.

[C-LEIGH RACING]

370r, while you have that cylinder off, do a presure check on the cylinder & head bolted.
Way to do that, get two pieces of 3/4" heater hose, what ever lenght you want & clamp a piece to the coolant outlet on the head & take the other piece & clamp to the coolant intake on the back of the cylinder. Now take something & plug the end of the hose clamped to the cylinder, be sure to clamp the plug your putting in the hose so it wont blow out.
Now, on the other hose on the head, get you a hose adapter, (those things like you use in a house water system) that has threads on the end & get a cap to fit on to that. Thake that cap & drill a 1/2" hole in the middle & insert a valve stem in the hole, just like you would on a rim.
Now, with all the ends clamped together & tight so they cant blow apart, take the cap off the hose end on the head, fill the hose full of coolant or water, (fill up the water jacket of the cylinder) turning it to get the air bubbles out & then screw the cap back on tight , then take the air hose & pump the cylinder up putting presure into the water jacket.
If you have a coolant leak somewhere, the coolant should show up wherever it is leaking.
When you pump it up with the air hose, dont pump it up too much, maybe 15lbs or so.
When I test a top end, I take a hot air gun & stick it into the exhaust & heat the cylinder up real hot, that way its just like as if the engine was running presure in the system & hot. If theres a leak it will show up.
Those cylinders sometimes are leakers in areas you wouldnt think of like aroung the outside of the sleeve between the aluminum & iron, & sometimes in the casting itself.
This little test will find it if thats whats causing the problem.
Neil

[jon370r]

Thanks for the sugestion C-LEIGH I will try that just to elininate another possibility. I didn't have any problem with loosing coolant and had treated the antifreeze with a stop leak shortly after running it for the first time because I have herd of these cylinders being porious and leaking through the casting.
Being of high reguard in the 250r engine building and if you don't mind me asking what would the effects of to much exhaust port duration be and what would you concider to much for a 350 PV cylinder.

[dober250R]

170-175 sounds low on a brand new cylinder...............

[spent21]

mine was at 175 new. on a 250r, 180psi is the transition to race fuel.

[hang1p]

when you get a 350 cylinder for esr with a 55r dome like me and jon have 175psi is exactly what your supposed to have

[C-LEIGH RACING]

With the PV, you could realy cut the exhaust port roof high as you wanted like a drag port set up, say to around a 84 to a 82 degree opening. The PV will take care of the bottom end to midrange.
I dont remember where you said you got that top end from, but what type of PV assy does it have on it, a Rotax one or a custom built one like ESR has.
I worked on a ESR PV cylinder some time back, & the owner said it had no bottom end, checking the porting it degreed out where it should have had bottom end & no top end. What I figuared it to be was the PV opening to soon, I cut a shim to go in the PV sorta stiffing up the spring a little & shipped it back.
Havent heard back from him yet, but that should have cured that problem.
Neil

[rebelbanshee]

what ever happend with this>?

[250r4life]

Originally posted by rebelbanshee
what ever happend with this>?

his 350 engine is sitting on the shelf, and he has a spare 250 motor in... i asked him a couple days ago

[jon370r]

I will be putting it back in the quad soon to bring up to the Engine builder for him to play with it to figure out what the issue is. He seems to think its the timing but I played with the timing with no result. I got a Hinson adjustable timing plate just for the ocasion.

[hang1p]

man it's been fun kicking jon's butt since his 350pv has been on the bench and he's running a 250pv, he's been kicking my butt for years

[sandspanker]

:) I had the same concern. It turned out to be the flywheel. ran fine cold, after warm up it would start cutting out. swapped it out /process of elemination. ran awesome after that. :D might be a good thing too check.

[jon370r]

I swappwed several different ingitions including CDI, flywheel and stator setups with no noticable improvement.

[beerock]

so you say you took the exact bottom end and put the 250r cylinder on it and it ran fine? damn has to be somethin with the cylinder, but you said your other 350 ran crappy too? i dunno

ive ridden some esr motors with drag ports and they dont go until your past 3/4 throttle to get them whined up strange problem

maybe there is a hole in the cases from the boring of them to allow the 350 cyl to fit? some people use epoxy to cover the holes up and it comes loose and falls out.

[C-LEIGH RACING]

jon370r,
Is this Chris R from Il.
Neil

[RadZuki]

Don't know why for sure but the Honda's seem to run better with the gap tightened up? Weak primary coil or secondary coil(spark plug wire coil) or weak CDI???
If all else fail's try the Janssen Motorsports HOT Coil they used on PSI 425 big bores, it might help out! I did not read all the posts so if you tried a diff. secondary already, try jetting!!!

Beerock PLEASE check your "PM" inbox and respond to my shock questions!
Thanks,
Rad.

[snono]

Hey there c-leigh. I am Chris R from IL. I am still pretty disappointed in my esr 350. Been looking at one of those saber cylinders but I hate to put more money in a cylinder than what you can get for a complete 250r quad. Did you try calling a while back?

[C-LEIGH RACING]

Originally posted by snono
Hey there c-leigh. I am Chris R from IL. I am still pretty disappointed in my esr 350. Been looking at one of those saber cylinders but I hate to put more money in a cylinder than what you can get for a complete 250r quad. Did you try calling a while back?


Yes, best I can remember awhile back I did try, things running together a bit around the shop from being so busy. Be glad when the national & local races are over.
Anyways, I found out somemore about those ESR valves.

The ESR valve picks up its operating pulse from the center of the blade valve itself & is more constantly under presure than any of the other types of valves system.
I beleave the only way to cure the problem would be to have the cylinder drilled, a operating pulse hole down through the block just like a CT or LA Sleeve cylinder has & then use a CT PV assy or one of the old model Rotax valves.
The pulse hole is on the back side, behind the valve up in the exhaust port tunnel & wont have as great a pulse signal as what the ESR is getting & would cause the valve to open slower & give better bottom end.
Keep this in mind, you have a good cylinder just need some minor details taken care of to make it operate right.
Neil

[jon370r]

C-LEIGH,
What would an exhaust port height at 205 degrees do to the performance,even with a powervalve?

[C-LEIGH RACING]

Originally posted by jon370r
C-LEIGH,
What would an exhaust port height at 205 degrees do to the performance,even with a powervalve?

If it has a CT or a Rotax valve assy on the cylinder, at 205 duration, about 3/4 up the rpm you better be ready to ride.
With the ESR valve, you may as well be on a stock stroke ported banshee cause thats what it will feel like.
Neil

[beerock]

have you really tried ringing the motor out? I know the esr motors are like light switches some tmes they wont come on unless you wait till past 3/4 and then BAM. if the motor is pushing the PV uptoo quick. then perhaps you could change to a heavier or lighter PV spring?

[jon370r]

Yes, I ran it hard when I had it in and it would never run clean no matter what I did to it. I will be putting the engine back in the Quad on monday and will try a few more things before taking it up to the shop that ported it for his ideas.

[jthunder31]

Here's a new thought on the original subject of this post. I'm looking at the pic of your motor on the first page of this thread, and can't help but notice the dip in the fuel line. It looks a little too long, and at extended high RPMs you may be starving your engine of fuel without a straight shot to the carb.

Why do I know this?

Because it happened to me!!!!!!!!:D

Worth checking.......