700 fusion tps question/low speed bog

TriumphoverU · Jan 21, 2012

So I set my tps per the video, and then adjusted the final reading to .93 for low elevation but when I start the sled the idle is around 2300 rpm. Have not been able to find any air leaks, TB boots are good, plugs seem to be a nice light brown color. So while the sled is running I backed out the idle stop screw to lower the idle rpms to 1500 rpm. Am I missing something when setting my tps? I built the tps tool with directions from this site and with a new 9v battery I am getting 5.01v through the home made tool.

I know my base tps voltage is now less than the .93 I started with because I lowered my idle with the idle screw. Do you think this could cause my low speed bog/flat spot?

The sled runs great from idle to 3600 rpm and above 4400 rpm but has a bog/flat spot between those rpms. No check engine light, new plugs, new plug caps, new fuel filter, fuel pressure is spot on, and compression is good.

Any other ideas? Sled is a 2006 fusion 700

Z-Man · Jan 21, 2012

exhaust valve sticking or bellow has hole possibly.

TriumphoverU · Jan 21, 2012

Z-Man said:
exhaust valve sticking or bellow has hole possibly.

I started to think the same thing too, so I cleaned the valves and inspected the bellows, but then realized the exhaust valves dont begin to operate until 6800 rpm, so I kind of ruled that out.

Is that normal to have to adjust the idle like i described once the sled is running?

Z-Man · Jan 21, 2012

Not sure where you got your info but if your exhaust valves don't open till 6500 rpm your engine will run terrible. The valves are designed to aid low end torque by making the exhaust port smaller. I had a hole in mine yesterday and it was extremely boggy when I tried to hammer the throttle at low speed. On my 1000 cc bike I took the valve off completely and the m1000 guys remove them too. I think you could probably take them off a 900 with little negative effect too but I don't know anyone who has done it.

RED BARRON · Jan 21, 2012

were your throttle bodies nice and clean when you set the base tps setting. i set mine not long ago and when i was finished i cleaned the tb's real good and when i double checked tps it was way off. reset after cleaning and runs better than ever. hope this helps

TriumphoverU · Jan 21, 2012

Z-Man said:
exhaust valve sticking or bellow has hole possibly.

Z-Man said:
Not sure where you got your info but if your exhaust valves don't open till 6500 rpm your engine will run terrible. The valves are designed to aid low end torque by making the exhaust port smaller. I had a hole in mine yesterday and it was extremely boggy when I tried to hammer the throttle at low speed. On my 1000 cc bike I took the valve off completely and the m1000 guys remove them too. I think you could probably take them off a 900 with little negative effect too but I don't know anyone who has done it.

The info came from the service manual. The valves stay closed until 6800 rpm when the computer sends signal to the VES solenoid to open the valves. Maybe I'm reading something wrong, but I'm sure thats what it said.

But if i hammer the throttle on mine it runs great, it only has an issue if i'm going a slow steady speed say 15mph with the rpms between the 3600 and 4400 rpms and then it acts up like its bogging.

Z-Man · Jan 21, 2012

interesting, guess i was wrong on that one. Seams strange they would plug exhaust till 6800 on a sled that only runs 7400. Like many of the guys on here I don't use the exhaust valve solenoid.

TriumphoverU · Jan 21, 2012

Z-Man said:
interesting, guess i was wrong on that one. Seams strange they would plug exhaust till 6800 on a sled that only runs 7400. Like many of the guys on here I don't use the exhaust valve solenoid.

I tried to plug the hoses on my sled but didnt notice any improvement so I put it back to stock. Did you have to change the VES springs to a different color to make it work properly?

Z-Man · Jan 21, 2012

TriumphoverU said:
I tried to plug the hoses on my sled but didnt notice any improvement so I put it back to stock. Did you have to change the VES springs to a different color to make it work properly?

nope, just plugged them.

TriumphoverU · Jan 24, 2012

Ok guys, I re-set my TPS this time using a different volt meter, still having the same problem. The sled idles at 2300 rpm when the tps is set to .93 volts. I followed the video/manual to the "t"

The sled still runs great above 4500 rpm and idles great although higher than spec. Could this be a bad TPS? Any light throttle pressure and the sled just bogs.

The sled has new parts as described in the original post, and the exhaust valves have been cleaned and the bellows inspected. Everything appears to be in good working order, and now I'm getting frustrated.

Any thoughts or ideas?

mtbroncrider · Jan 25, 2012

have you tried re-adjusting the idle set screw on the throttle body?
I know thats why mine was idleing way to high last year.....jam nut got loose and allowed it to adjust up
reset and lock tighted down....no more hi idle problem

guidoxpress · Jan 25, 2012

Could be a flat spot in the tps

I've had to lower the idle on a few 900 s after I rest the tps

Some will run great at 2000 rpm and others down to 1400..and some won't stay running if in between..

TriumphoverU · Feb 10, 2012

Well I replaced the TPS and the TPS harness and I've still got my issue. What rpm does the ecu switch over from the low speed to the high speed injectors???

guidoxpress · Feb 11, 2012

TriumphoverU said:
Well I replaced the TPS and the TPS harness and I've still got my issue. What rpm does the ecu switch over from the low speed to the high speed injectors???

well, i now have the same issue as you...

built a sled for a fellow snowester and set TPS, new boots, new filter along with other mods...didnt do the TPS harness but wish i just did anyways...

but also have a bog off idle until i get it about 4000rpm then sounds good...but doesnt react anywhere near as good as mine does..

did everything i vcan think of to fix bog, and now the reverse isnt working AT ALL either..doesnt even attempt to work..

gonna switch the ECU, and also see if i can get a gauge to check fuel pressure...??? stumped right now also.

Newfusion900 · Feb 11, 2012

Hey guido! I read in another post that a clutch spring may cause a bog? If it can cause that it may give you a problem with your reverse also. Might be worth taking a look at.

guidoxpress · Feb 11, 2012

Newfusion900 said:
Hey guido! I read in another post that a clutch spring may cause a bog? If it can cause that it may give you a problem with your reverse also. Might be worth taking a look at.

hey bud.

has a freshly balanced clutch and new springs in primary/secondary also..

been reading for 2 hrs and wrote down everything i could find that has caused a bog, lol.

--ECU (have one to swap out)
--Stator wires chaffing (the inner ring on his flywheel was loose and just barely slit the wire on the harness but i taped it up but maybe i should have looked in the harness more??)
--throttle safety switches (never looked at them)
--TPS harness (i did not replace yet)
--fuel pump/or fuel regulator (i did not check yet)
--shorted hand warmers (new ones installed)
--bad voltage regulator (have one to swap)
--bad injector (swapped PTO side only due to losing low rod bearing already)
--wire on air temp sensor (did not check yet)
--chipped reeds (i think i checked them over, but cant remember)

am i on the right track, LOL!!!

TriumphoverU · Feb 12, 2012

I'm leaning towards a bad fuel injector on my sled. mine only has a problem from about 3800-4400 rpm which is right about 20 or 25mph. So riding in town is not so easy.

I'm leaning towards the low speed fuel injector (which i think is the one in the jug right?) has low fuel flow.

But I'm curious guido as to what you find.

guidoxpress · Feb 12, 2012

TriumphoverU said:
I'm leaning towards a bad fuel injector on my sled. mine only has a problem from about 3800-4400 rpm which is right about 20 or 25mph. So riding in town is not so easy.

I'm leaning towards the low speed fuel injector (which i think is the one in the jug right?) has low fuel flow.

But I'm curious guido as to what you find.

i might not get to his sled till next week unless i get a second on tues to meet him and do a few quick checks.

if your having issues at low rpm, it would be your injector thats in the case..the upper injector in the cylinder is used around 5800 rpms-up or so..

TriumphoverU · Feb 12, 2012

guidoxpress said:
i might not get to his sled till next week unless i get a second on tues to meet him and do a few quick checks.

if your having issues at low rpm, it would be your injector thats in the case..the upper injector in the cylinder is used around 5800 rpms-up or so..

well then that wouldnt make any sense to be my problem if the injectors dont switch over until 5800 rpm.

I need to figure out what changes on the sled at 4400 rpm. whether it is injectors or or exhaust valves, timing or something else. whatever it is, it clears up at 4400 rpm.

700 fusion tps question/low speed bog

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