MadMax's Carb headache

[AlanB]

Hi Max,

Sounds good, but I would still suggest that you try some carbs!

My bike has totally stock internals and is about 4hp short of Maxi's output for a total expenditure of around £250........ including the K&Ns and the dyno time.

Take that as a baseline, and then add your other mods; where do you think you will end up?

If you do indeed have the access to the same facilities as Cody used, I would LOVE to see you try these carbs, (or something similar!) and put some directly comparable figures on the table.

They work!

AlanB

[madmax-im]

To clarify the point of this custom cut profile big bore kit is obtain a compression ratio of 10:1...

[AlanB]

Hi Max,

Your custom bore kit sounds good; I would like to follow you along that path! It sounds like it would give the best possible combination of parts, especially if combined with the earlier (lumpier!) cams.

It will be a monster with the (modded) XS carbs, But it will still make more power, and be easier to tune on the dyno with modern carbs.

I am not trying to criticise what you are doing; You seem to be very well informed. I am just suggesting an additional, well proven route to a few extra horses.

The shop which pointed me to this conversion had done dozens of CV equipped bikes the same way, mainly on GXS Suzukis, and Kawasaki 1000/1100s (plus my XS11! LOL!); all with similar results. I have ridden several, all were good, which is why I went with the conversion on my own bike.

I know that Cody (and presumably his tuner?)did not like the idea of this work, and had frequent disagreements with at least one other member who had fitted later type carbs, so I assure you that I am not abusing your work, only trying to help.

As I said before, enjoy your tuning, however you go about it!

AlanB

[DiverRay]

TC, I think the problem is the '82 head has MORE ROOM than the early version!! THAT is what Cody was up against. I WAS IN THE TUNNEL when he ran the HD, and Zilla IS fast! The later heads in the XJ have a bigger chamber, and a LOWER compression ratio than the older heads.
I'm looking for an '82 head for my winter project, as it will have PRESSURE FEED for the intake.
madmax-im,
BUY THE NEW GEARS!! If you are going for HP, go for the new gears. There is ALSO a washer you need to put in on the CLUTCH mechanism between the crank and the clutch. I don't remember the thread, but do a search!

[TopCatGr58]

Hey Ray,

The 82XJ uses the same valves as the 80-81, and so I thought the 82 had the same dome as the 80-81, not the earlier 78-79 ones with the smaller valves!?

The XJ has the same bore/stroke, and the same COMP ratio of 9.0:1, same as the 80-81 series engines, vs. the earlier 78-79 which has the 9.2:1 ratios due to the more domed pistons, smaller head chamber dome!

SO...this was/is why I was making the argument/tech. discussion about the comp. ratio with the big bore kits on the later engines/heads. I am assuming that since they, the XJ and the SH have these same values and parts, that the chamber isn't changed, just the addition of the YICS in the head!
T.C.

[madmax-im]

AlanB;...In rereading the entire thread i realized a few things i didn't address..first off i appreciate the advice on using modern carbs...I have no reason to doubt that they work well.I would like to add them to my XJ11...Im sure they would enhance the situation greatly... You asked ..if combined with slingshot carbs and my mods what would I likely end up with???Well how 'bout a Saturn 5 booster rocket!LOL...more than likely a conservative figure would be abt 110-115 hp and 72 ftlbs torque.But in all reality here i am not looking for a top end barn burning race extreme machine....I want it for Sport/Touring and have the empasis on the Low and Midrange grunt in the engine's powerband...I will be doing alot more research and learning before I go ahead with my big project here....Thanks for all your great input and advice....Bennie....hence... BNE

[madmax-im]

one more point to clarify

I need to clear up a discrepancy in my posting.I have just been made aware that an email I reccieved from the gentlman in OK who will work on Madmax...he inadvertantly quoted me a price of 4-5 thousand for replacing all of the tranny gears and in actuality thtat was a typo error and the actual cost for the tranny gears and labor would be $1000.So PHEW!Glad thats cleared up.I would not want someone's good name tarnished due to a lack of the facts...the whole job of doing the engine big bore and the tranny will run total of $4-$5 K...

[AlanB]

Hi Max,

The later carbs DO give a top-end power lift, but the really big differences for me were in the throttle response and in the midrange power; The bike felt years younger, idled cleaner, and pulled really strong from low revs.

I would definitaly recommend a more modern set of carbs for the type of riding you want to do!

This is genuinely a modification with no downside.... unless you are seeking originality.......

AlanB

[GNEPIG]

Maximan did change the carbs on his bike. He bought them from the Stillwater shop, they were 36mm CVs from an FJ 1200. Tho the FJ carbs are not as good as the ones AlanB speaks of, they are still better than the stock ones. And these are part of the reason that Maximans bike runs so well.

[madmax-im]

Well Guys that just abt clinches it for me....Alan I'd like to know more abt your carbs and where I could get a set..?You can bet that i will go this route.What carbs would you reccommend?And how much would they run?One of my complaints abt Madmax is that he isn't idling as smoothly as he could. Throttle response and crispness of the throttle is sluugish and the bike is tuned so that most of the power is at the upper end of the powerband.I always need high revs to launch from a standing stop...and then i run into too much acceleration in 1st gear and then I get the tranny 1st to 2nd slip...Then he is cold blooded even in the summertime..it takes abt 10 mins for him to start running smoothly.

[AlanB]

Hi Max,

Sounds like you have a problem with the existing set-up! this is an 1100cc motorcyce; it should have plenty of power to pull away easily with a windjammer fairing, a full set of loaded luggage, and a heavy passenger. As a naked bike, it should go like a shot dog!

If I can assume that the bike has had a basic service (plugs+ oil changed, Timing and valve clearances checked!) then it has to be carbs! sounds like the bottom-end is lacking, the rest is OK; if so the problem is in the pilot circuit.

I would sort it out and test the true capabilities of the bike before thinking about a $5000 tune job........

There are probably more threads on carb cleaning and setting than anything else on here; Start with the Tech tips and then try a search; If you think you need more help than that, just put up a post to ask......... There are others on here who are far more expert than me on the original carbs.

My original carb write-up is on the UK site CLICK HERE!

Hope this helps......

AlanB

[randy]

Hey, Max

Good rule of thumb to remember:

-lean problems get better as the engine warms up.

-rich problems get worse as the engine warms up.


Sounds like it's runing too lean, like alanb wrote, the pilot circuit being clogged can cause that. Your carbs probably only need a good cleaning and synching.

[madmax-im]

Alan and Randy;
Last year before I had any work done on Madmax..he was fine.I mean low end acceleration was easy.No hi revs just normal revs...Then last Spring I had some mods done.. I didnt do the work myself but I had a new MAC 4 into 1 exhaust installed,a Stage lll carb kit,had the old airbox out and put on4 individual K+N
air filters.I also had the clutch plates replaced and new springs as well.The very first ride after all the mods and the first thing I noticed was that under the type of acceleration I had been doing..was now inadequate and the bike was lugging...until I figured I needed more RPMs' to launch from a stop.Well then I gave it more RPMs to get going but it still would not be enough and the bike would lug again....then I adusted my throttle hand to the tune of 3500-4000 RPMs' and tried a launch....it worked ...but then I started to notice the 1st to 2nd gear slip and thought WTF?So prior to theses upgrades,I had never experienced these problems.I appreciate your comments abt the state of my carb and you can bet I will be reading up on this alot more...thanks for the link Alan....

[madmax-im]

$5000 tune up?

Well Alan....I find it amazing that with only refitting slingshot carbs off a Suz.GSXR750...you were able to obtain numbers close to what Maxman obtained with a lot more work and money too!So I really do Thankyou for opening my eyes to the potentiality with a modern carb swap.You know I will be doing this FIRST!I might not need to go the route that I was originally planning on...And while I am not a cheap bastard...I do tend to waste my money ...sometimes.I just dont want to do so here in this case.If I can get the desired results or even close to the desired results without a $5k investment.....then why would I be crazy enuf to spend that kind of dough...??So once again mucho THANKS...i will keep you all updated...Now to search for some modern carbs...

[randy]

Alan,

based on your set-up, I'd suggest that you:

Get rid of the stage II kit, go back to stock jet type. Your stock jets were 112.5, so with the 4-1 and the K&N, go up 2 sizes to 117.5.

Make sure your floats are set correctly, refer to the manual, I don't know the setting for your 82XJ.

That should get you to a starting point.

Synchronize the carbs and final idle and transition adjustment can be made with the pilot screws.