900 cat big bores

[unclemark]

Hi im looking fore guys running a 1100 hooper, 1150 cutler or a 1150 union bay big bore baste off the 900 cat motor. My 1100 hooper is giving me tuning fits any help would be grate THANKS


Mark

 

[icr]

I'm no expert....but I did stay at a holiday inn last night.

What are you having trouble with? Clutching, jetting, coolant color choice?

 

[zaxxcmx925]

Low bog

YO MARK I THOUGHT YOU HAD IT FIGURED OUT SATURDAY
MAYBE NOT,OR IS IT A DEFERENT BOG?
MAY BE MORE AND A SHOT CASK 16 HELP YOU FIGURE IT OUT HE HE

 

[unclemark]

I'm running a 1100 Hooper with custom fitted jawz pipes i put in a IQr chassis.
the problem I'm getting is a nasty low end bog when the motor gets hot its like its running on choke it stutters really bad to the point it wont go .but when it over comes it it hall azz .so on the top end it runs really good. i was running 55 pilot jets now I'm down to 35 it helped a lot but the bog is still there so now i set the needle in the center clip, main jet 500, pilot jet 35,and starter jet at 130 But the dam bog is still there so i was hoping to compare to some one who runs a big bore in the state. ow yea the carbs are stock bored to 42 .

Thanks

Mark

 

[icr]

When you say low end what RPM and throttle position are you at? What fuel are you running? Premix?

 

[unclemark]

it has a bog when i grab a hand full o throttle but when it over comes it it hallz azz some times when under load it stutters and has a hard time over coming it i was running avgas with premix 32-1.

 

[icr]

It only bogs when the engine is hot? Airbox or filters? Are you running a thermostat? Exhaust valves?

 

[spring snow hero]

what is the scoop on your clutching setup? is it loading up too soon?

 

[unclemark]

It only bogs when the engine is hot? Airbox or filters? Are you running a thermostat? Exhaust valves?

yes on the thermostat ,no on the exhaust valves the hooper cylinders dont have the valves ,with filters haven't had time to build a air box yet, it has the lowend bog even when the motor isn't hot

what is the scoop on your clutching setup? is it loading up too soon?

maby it is it engages at around 3800 rpm I'm thinking of putting a stiffer spring in

Also i pulled the head and getting some detonation the inner o ring was shot . checkout the squish its at .0975 these heads are cut by hooper for sea level and avgas. called John hooper he said it could be the pipes to much back pressure. he said 36mm should be the smallest opening where the pipe meets the stinger.i measured it and it is 36mm so thats not the problem

 

[icr]

Sounds like you're treating this as if it's a rich bog...has this been established? What do the plugs look like at low RPM...does it bog if you ease into the throttle? How's it run if you hold it at 1/4-1/2 throttle?

Do you have EGTs?

 

[unclemark]

Sounds like you're treating this as if it's a rich bog...has this been established? What do the plugs look like at low RPM...does it bog if you ease into the throttle? How's it run if you hold it at 1/4-1/2 throttle?

Do you have EGTs?

yes on the EGTs. the reason im thinking its a rich bog because it gets worse when the motor gets hot. it bogs at the 1/4-1/2 then it over comes it .now this gets allot worse when its hot . now when i pulled the head it looks like its lean ?? I did have to run it 3/4+ throttle all the way back to the truck. it would stutter very badly and not go at all at 1/4-1/2 throttle. according to the EGTs i do get hotter when climbing wide open .

 

[icr]

I'm fighting a lean bog at 1/4-1/2 throttle is why I ask. My EGTs spike around 6000 RPM...I raised the needles and it cleaned up that spot but was excessively rich everywhere else in the powerband...now I'm sanding my needles to compensate.

Mine also gets hotter on the EGTs when climbing wide open...I just jet accordingly.

 

[unclemark]

I'm fighting a lean bog at 1/4-1/2 throttle is why I ask. My EGTs spike around 6000 RPM...I raised the needles and it cleaned up that spot but was excessively rich everywhere else in the powerband...now I'm sanding my needles to compensate.

Mine also gets hotter on the EGTs when climbing wide open...I just jet accordingly.

Ted from Terra alps racing told me to get needles from a 03-05 vertical escape 800 and that would be the ticket for the low end lean bog.

i think i will jet up to 520 drop the needle and put a stiffer spring in so it doesn't load up to fast and run up to hatcher's for a test run and see what she tells me .

Thanks
Mark

 

[icr]

Ted from Terra alps racing told me to get needles from a 03-05 vertical escape 800 and that would be the ticket for the low end lean bog.

i think i will jet up to 520 drop the needle and put a stiffer spring in so it doesn't load up to fast and run up to hatcher's for a test run and see what she tells me .

Thanks
Mark

If it was me I'd try one change at a time and leave the mains alone since it clears out at full throttle. Maybe the spring first since that's easiest to change in the garage then adjust jetting on the hill.