Won't rev

[texas-ss-tornado]

Been working on a 90 model, it's got a Stage 7 on it, Vboost eliminated completely, 4 new K&N individual filters. Anyhoo, just did a shotgun treatment on them, had replaced the fuel tank and thought I had some garbage in them, actually they weren't that dirty. The darn thing just won't rev, it starts and idles, but when you give it alot of throttle it just falls all over itself, if you nurse the throttle, you can get about 7K out of it, but that's it. Can't get it to redline, seems to be running on all 4 cylinder, I think the fuel system is working well, seems to be holding pressure, no leaks. I'm beginning to think electrical now, going to try and see what it's putting out voltage wise. Any ideas?

 

[PATMAX]

I wonder if you can eliminate electrical since it is igniting fuel at 7k rom. A bad stator would not affect spark would it? It sends the signal to excite the coils doesn't it and send a charge for the R/R to charge the battery yes?
Any chance you swapped the TCI with a known good one? Just sounds like too much fuel or weak spark to me.

 

[texas-ss-tornado]

Well, for grins, I put a stock airbox on it, and it runs 10 times better! Rode it around the neighborhood, the top end is still weak, but at least it revs now and will approach redline. Wonder what could be going on with the carburation on this bike, DannyMax had them apart and verified it had the Stage 7 kit in it. I tried to hook up the individual K&Ns, just like it had when I got it, but it ran like dog doo doo. Interesting.

 

[[email protected]]

Are your vent tubes clear and properly routed?

I've heard similar issues caused by pinched or missing vent tubes. That has typically been with a stock airbox though.

 

[D-Max2012]

Dood, I feel your pain..
I've been dealing with a 91 with the same problem.
I broke down the carbs 3 times, (last time was for an Ultra Sonic cleaning)..
Thought I had it nailed down when I found my boots were cracked.. It made no difference. Tried for 3 weeks to clean my tank by siphoning the crap out if it.. Still had rust and crap getting to my carbs. Finally got a tank off EBay and Coated with KBS.. (Came out great), no crap in my filter or carbs.
It could idle fine, but when you rode it, it would stumble around 2-3k in 2nd, no power anywhere higher. I read this test a guy on this forum posted. To test if the bike is lean or rich, carry two pieces of duct tape on you next run. After a test run, cover 1/2 of each air intake opening (stock air box). See if it gets better or worse. If better (running lean), if worse (running rich) without tape in place. (Sounds like you had the same result when you put the stock back in place).
I tried it and it turned my little canary v-max into a mad assed eagle.
So, it was running lean with no tape (too much air in the mix). That lead me to look at all the jets that the previous owner had in there. I found out that the P.O. had 3 Mukuni 118 Main Jets and one DJ120 in there.. Looking at the carb setup area on this site, most are running Mukuni 150 - 152.5 (some 160) but, in that area. Changed them out yesterday to stock settings in manual. Carbs 1 and 3 @ 152.5 and Carbs 2 and 4 @ 150. BIG Difference.
Check your carb mains.. Just to be sure.. This **** can drive you Nucking Futs.

 

[Rusty McNeil]

I don't know if this isrelevant but when I first started trying to sort the new engine out it wouldn't take throttle at all past about 6000 rpm. Turned out to be way the hell rich.

I wouldn't bet that was your problem since it probably ran fine at one time?

 

[texas-ss-tornado]

It had the Stage 7 on it when I got it, but it never really ran "good", I assumed it was junk in the carbs, had them cleaned out twice, that's where I'm at now. I "know" it shouldn't run right with the Stage 7 jets, 4 into 1 Kerker and a stock airbox, but it runs ALOT better than it did with the individual K&N's and the other Stage 7 plumbing hooked up. At least it's ridable now, I may run a tank of good gas through it and see what happens. I really would like to run the invidual K&N's, after all, they cost me an arm and a leg and with the correct jets and 4 into 1, is supposed to be the best setup for performance. Not to mention the V-Boost being totally eliminated!!!!

 

[johnpclynch]

Do the carbs have air correctors?
I had a similar issue while trying to jet for an opened up airbox until I put a set of Morley's air correctors in

 

[dannymax]

It ran real nice when I was setting the idle & sync....don't remember what it had for jetting or if it had air correctors or not but it's sounding like a tuning issue.

Did you have to mess with the pilots John or did the idle smooth out with the airbox?

 

[johnpclynch]

It ran real nice when I was setting the idle & sync....don't remember what it had for jetting or if it had air correctors or not but it's sounding like a tuning issue.

Did you have to mess with the pilots John or did the idle smooth out with the airbox?

I didn't go near the pilots, I only put in the stage 1 kit, K&N + air correctors (plus that massive hole in my faux cover)

 

[dannymax]

I didn't go near the pilots, I only put in the stage 1 kit, K&N + air correctors (plus that massive hole in my faux cover)

I was asking Texas-ss, his name is John also...:biglaugh: We had talked on the phone about an idling issue.

 

[texas-ss-tornado]

Danny, I didn't touch the pilots. All I did was take it all apart and blow out everything with compressed air, they weren't as dirty as I had expected, which is good, because I know my new gas tank is clean. The bike idles OK, better now with the stock airbox than with the K&N's, but top end is weak, doesn't pull hard like a VMAX should. I replaced the coils yesterday just because I had an extra good set, wanted to eliminate that. I'm not 100% sure the charging system is up to snuff though, but it's a fresh battery so I don't really that's the issue, pretty sure it's carbs.

 

[johnpclynch]

I was asking Texas-ss, his name is John also...:biglaugh: We had talked on the phone about an idling issue.

There are too many Johns/Seans around :biglaugh:

 

[dannymax]

There are too many Johns/Seans around :biglaugh:

Damn few Danny's tho....which is probly a GOOD thing!! :rofl_200:

 

[dannymax]

Danny, I didn't touch the pilots. All I did was take it all apart and blow out everything with compressed air, they weren't as dirty as I had expected, which is good, because I know my new gas tank is clean. The bike idles OK, better now with the stock airbox than with the K&N's, but top end is weak, doesn't pull hard like a VMAX should. I replaced the coils yesterday just because I had an extra good set, wanted to eliminate that. I'm not 100% sure the charging system is up to snuff though, but it's a fresh battery so I don't really that's the issue, pretty sure it's carbs.

I agree, it sounds like jetting. Do they have air correctors?

 

[texas-ss-tornado]

I agree, it sounds like jetting. Do they have air correctors?

I'm not sure what you are talking about, please be more specific. These are the carbs you cleaned for me about 9 months ago, do you remember them?

 

[dannymax]

I'm not sure what you are talking about, please be more specific. These are the carbs you cleaned for me about 9 months ago, do you remember them?

Yes I remember them, but not the specifics.

Here's a pic of the air correctors, they go in the top of the carbs next to the PAJ1 and restrict the amount of air. I believe they are necessary with stg7 set ups.

 

[texas-ss-tornado]

I blew air down those holes for sure, and it's clean as a whistle.

 

[dannymax]

I blew air down those holes for sure, and it's clean as a whistle.

PM sent

 

[dannymax]

I blew air down those holes for sure, and it's clean as a whistle.

Didn't mean they were dirty John, the green pen points to the main air jet location, air correctors are little brass plugs with very small holes drilled in them to cut down the amount of air going in the air jet.

Are the air correctors in the main air jet?