Re-jetted a 98?

[nightowl]

Has anyone out there re-jetted their '98 Steamer?  For those who don't know they switched from Mikuni carbs to Keihin carbs for the one year and then went to fuel injection in '99.  The K&N jet kit is for the '94-'97 models.  I have seen Blake's Tiger page where he drills his jets and changes the slides but I would rather not make irreversible changes; in case it fails I can always go back to stock.  So I'm wondering if anyone has ever just bought larger Keihin jets, maybe put a shim under the needle, opened the right side snorkel, etc., etc..  If so, what was the final recipe after all the tweeking?



Thanks

Scott

[Deltabox]

Well, basically, the engine of the T400 steamer is similar to the T300 engine (Speed triple, Daytona, Sprint etc), except for the cams, exhausts, CDI unit and the snorkel.

So, if you open up the 2nd snorkel, you can use whatever carb settings the T300s use as a starting point (as long as they use the same carbs, of course).



I did this on my '94 steamer (used a shop manual for a Daytona to find the carb settings). I think it might be running a bit rich, but that's just a gut feeling. I'll probably go for a dynorun this year to get it properly sorted.

[BR]

Yup, I've seen Blake's site and his write up on his bike.  I wish he'd update it.  Anyway, why do you want to re-jet?  Blake did it because he didn't like the roll-on lag at freeway speeds. I don't have an issue with that because I don't find myself "snapping open" the throttle all that much.

My '98 has the Yoshimura cans and it always ran ok but popped a bit on trailing throttle and was cold blooded in the mornings (even with OEM cans on).  My little 12 mile each way commute got me ~42mpg.  However, I've since shimmed the needles ~0.025"and adjusted out the idle mixture screws 3.0 turns (under the aluminum plugs on the bottom/front of carbs).  My airbox is brand new and I've got one of the intakes still capped off.  However, my bike has been on an "extended service" for the past 6 mos while I've completed valve adjustment, new airbox, carb work and general tinkering.  So.... I actually haven't ridden it since I've made these changes.  It sure sounds good so far, starts right up, idles fine with the Yosh cans on and I don't expect any surprises when I do start riding it.  What I DO expect is that it will not be so $###!@@ cold blooded in the morning and I won't have to keep the choke on full just to pull away normally.  So, jetting-wise, these are the only changes I've made or expect to make.



Brendan R.

'98 BRG Tiger (30K miles)

San Jose, CA

[nightowl]

I'm also re-jetting for the poor low end roll-on performance.  Mine was/is pretty bad.  It would surge badly just on a slow roll on coming out of a turn.  Top end perfomance seemed fine though.  Also its very cold blooded and hard to start.   I have the stock pipes and airbox.  I took the airbox apart and found a very nice foam filter so I cleaned it and oiled it with Uni filter oil.  I resent the idea of having to buy a whole new airbox just to change a filter.  Damn expensive too.  I also took the carbs apart and flushed out all passages with spray carb cleaner.  None of this helped much.  Before changing jets, I experimented with resticting the air flow using a bit of duct tape to partly cover the snorkle.  Low end roll-on improved dramatically but of course the enigine would not rev past 6000 at all.  So it was OK at high end but starved for fuel down low.   I then drilled out the mixture screw covers.  Stock settings were 2.5, 1.5, and 2.1 turns out.  I have done a lot of trial and error adjusting of the screws to no significant avail.    Decided to try richer jetting.  Stock main jets are 98 and I went to  102.  Note that they only use even numbers.   Local dealer told me that 100 would be half a jet size up so I went to 102 on his advice.  Also shimmed up the needles using 0.025 brass washers.   The result was a slight improvement in the roll on problem Better, but the plugs would start to turn grey after 100 miles.  OK, 102 was too rich (but I never tried it with the second snorkle cap removed).  Did some digging on the net and found that the Mikuni web page has a neat guide on how to tune M/C carbs.   The same basic principles would apply to Kehin as well.   So I learned that high end is affected mostly by the main jet size, mid-range is governed by the needle position and shape, and low end down to idle is controlled by the pilot jet and the mixture screw.  [I'm oversimplifying a bit to keep this short but appears to be a lost cause.]  You can also affect mid-range by changing the shape of the slide but that's getting fancy.  Based on this wisdom, I went back to stock mains and kept the shims in.  Problem still there but getting better.  The guide also indicated that mixture screws work in the range of 0-2.5 turns out.  Well my stock settings were already close to that.  Beyond 2.5 turns, you have to go to the next size pilot jet.  Stock pilots are #38 so I bought #40 to try (again only even numbers).  This all took place last fall and I eventually had to drop it and do other things.  So now I'm picking up where I left off and hoping to get it straight so I can start riding in the spring.  Yes, I could take it to the dealer but I want to learn how to tune carbs so I'm going to fight with it a little longer.  I plan to get some carb sticks or vac guages so I can check the balance as well.  

 

Sounds like you are trying some of the same things.  Let's keep in touch on results.



Cheers

Scott

[BR]

Scott,

Well, you've dug into this jetting stuff a lot farther than I thought you had based on your first post.

About all I can add is that since you're obviously the DIY type, you should ensure that other aspects of your engine tune are in good shape while you play with the carbs.  That is, good compression, valve clearances checked and adjusted as needed, fresh plugs, clean airfilter (you did that), rubber carb boots are not cracked etc.

My original mixture screw settings were similar to yours but I may back them off from 3.0 turns to 2.5 once I get a few miles on it.  Naturally, the *best* way to set these are with an EGA (exh gas analyzer) but I don't know if this is considered std equip at most shops these days (prob not).  Btw, the EGA plugs into those little 10mm bolts on each of your header pipes.  As you mentioned, certainly get yourself a set of Carb Stix or equivalent.  I've had mine for years and it works great.  Having your carbs synched helps with a nice smooth idle and throttle response (but that's it).  I just did mine this past weekend...dirt simple!!!!

I should be back on my Tiger in a week or so and I'll report on my relatively minor jetting changes (mixture screws, shimmed needles, new airbox/filter which cost $60!!!).

Feel free to email me directly if you want.... mailto:breitz@cisco.com">breitz@cisco.com



Brendan

'98 BRG Tiger

[nightowl]

Brendan,



OK!  I look forward to hearing about your results.  What I am shooting for is to get the jetting right so it runs good with both air intakes uncapped.   That should translate to a nice power increase.  Plan to stick with stock exhaust.  Might be willing to go with K&N air filter if needed, which is why I'd rather not spend the money on a new stock one just yet.  



If you scroll down in this forum, there is a post on Tiger airbox mods where they mention how rejetting makes a huge improvement.   But I'm guessing that fellow has the Mikuni carbs ('94-'97) so I can't just use the same recipe.   There have also been some posts in the Yahoo Tiger group that mention the benefits of re-jetting.  Not much jet discussion in recent years though with the FI models predominating.  Anyway I'll post results when/if I ever get it running right.



Scott

[BR]

Hello Nightowl,

Here's my brief ride report as I finally took a test ride on my '98 Tiger after some minor jetting changes.  In short, all is good (but as you know, my changes were minor).

First ride was only a few miles but it was sputtering a little just off of idle under load.  At this point I had the left airbox snorkel capped and the right one open but had NOT installed that little tube and the angled outermost piece.  No reason.. just hadn't put them on.  But, I wasn't too thrilled about the prospect of pulling carbs again to investigate the sputtering if it persisted.  So, I re-installed the tube and angled inlet cap on right side and rode about 10 miles.  Sputtering gone.  Pulls to redline, smooth idle but still some minor popping on trailing throttle (I'll live with that).  Cold start was immediate and by the time I put on my gloves (helmet already on), I could pull away no problem and take choke off within a half mile.  This is considerably better than before as bike was very cold-blooded (even in 60F temps).  So, my goal of improving morning driveability has been met.  This also seems to demonstrate the sensitivity of the Tiger to minor airbox changes which does not paint a good picture for your goal of removing the airbox cap from both sides.  One other thing I failed to mention before is that I also removed the little in-line filter from the fuel line.  Assuming you still have the formed OEM fuel line to the carbs, you'll find it just above the T-fitting between #2 and #3 carbs.  You should remove it and put it a larger in-line unit just down-stream of the fuel valve.  I found a nice compact clear unit at local bike shop and it works great.

Beyong the minor carb tweeks I did, the carb synch, valve adjustment, new chain rubbing block and swing-arm protector have all contributed to making the bike smoother and more mechanically quiet as well.  I think my next project will be to seal the rims so I can go tubeless but that's a whole 'nother topic.



Brendan R.

'98 BRG Tiger

[Deltabox]

Like I said, opening up both snorkels is fine, as long as you use the jet/needle settings used on the Daytona 900, so you don't HAVE to experiment to get a decent running engine  :D  (just get hold of a shop manual for the Daytona).

Easy, cheap 'n cheerful, engine runs great, and no other mods necessary.

[TigerTrax]

You can really screw up if you don't think about what you are doing.



I drilled my main jets out and stuck a 4,àû advance in the timing.

Runs great.

LEAVE THE SNORKEL ALONE.  LEAVE THE AIRBOX ALONE



I'll have to look up the specs.... e-mail me off list.

[nightowl]

BR-  OK, good news on your mods.  Glad to hear its running better.  So with stock jets, aftermarket mufflers, stock airbox; the only carb change is shimmed needles (?) and its no longer cold blooded.  Interesting.



Deltabox- Thanks but I have the factory manual covering the all carb models (pre-99) and it shows the Daytona as using Mikunis.  If I had Mikunis I could just get the Dynojet kit.



TigerTrax- Hmmm, I never thought about timing.  But according to my manual, it is all electronically controlled.  There isn't even a static timing adjustment.  So how did you advance 4 degrees?  Did you move the pick-up sensor ever so slightly by reaming out its mounting holes?  



Yup, screwing up is why I want to re-jet rather than drill.  Then I can alway undo it.



On the airbox, it seems very strange that such small changes would affect the performance.   That would suggest that even a slightly dirty filter would affect performance.  I would think/expect that the bottleneck should be the carb inlets.  The box and filter should have minimal restriction in order to allow the carb adjustments to have direct control over engine performance.  



Well I'm going to keep at it and see if I can find a jetting combination that works.  I can borrow a CO analyzer and connect to the fittings on the header pipes.  The manual has target numbers for both the U.S. and U.K. versions.  Will post results if/when I get there.  Finding time to work on it is the real trick.



Cheers

Scott

[BR]

Nightowl,

I'll clarify a little:  stock jets, needles raised, mixture screws at 2.5 turns,  new airbox, carb synch, no mods to airbox or snorkel.  And yes, my cold start drivability has greatly improved!!  Bike runs fine throughout the rev range.  Only issue is that I'm hearing some very slight popping while engine is idling so I'd say one carb/cylinder is a bit leaner than the others.  #3 carb gave me trouble before so I'll fool with that one first (mixture screw).



Brendan

[TigerTrax]

Nightowl:



I simply purchased a 4,àû Advance Timing Disk from Factory ( that's the name of the company.  It takes about 15 minutes to make the swap.

RH side below the jug; Round cover.



PS... I actually purchased a set of stock jets ... just in case I screwed up when I drilled out the jets.



It leveled out the flat spot, gave me a little whack... I wish I had slipped the disk in B4 I drilled the jets ... just to see how it works with stock jets.

[BR]

Hey Nightowl,



What's the latest on all your jetting experiments for your '98 Tiger?

Not much here for me... I moved back in June, bike sat for 6 wks, wouldn't start, pilots plugged again, so it's all apart for some cleaning.

I had forgotten previously to ask you where you where buying your jets... I recently found that Sudco.com has the jets for our Keihin carbs but I need to order them through my local shop.  Prob going leave the mains at 98 but up the pilots from 38 to 40.



Brendan

'98 BRG Tiger

San Jose, CA

[apache]

Man, I must be lucky on my 97. It has 0 cold run issues, always fires right up. however it does seem a little doggy at 3/4 to full throttle when rolled on but I never go there much. I was amazed as mentiond at how bad it ran with the right side air box cap off, seemed to go like hell from idle to about 2500 rpm then just die. you couldnet even ween it up to 5K rpm, just wouldent go. I seem to get rocks and small gravel in my air box so I picked up a Uni sock filter and zip tied it over the opening on the left side. this will aid in stock filter life and it musta richened it up a scosh cause I swear it runs better now. Just a thought for you guys.

 In my experiance also most bikes are never jetted fat on top, theory is to pass emissions they run em at highway speeds only, like 1/3 throttle,5k rpm, 60 mph. thats where the wanna see good numbers to satisify the smog gods. Shimming needles and pilots usually take care of it. Also I spent many years employed at a major MFG of bike exhausts we also sold "jet kits". I can tell you from my own actual encounters on the dyno many cases of "generic jet kit" and exhausts caused the loss of many HP. To many figured if it sounded badass, it must be faster. Were better off using a logical start from other guys trial and errors.

[nightowl]

Hey Brendan,



I haven't done much.  My summer has been really hectic.  I did manage to put together some vacuum gauges (with buffer chamber and needle valve to smooth out pulses) so I can sync the carbs, and rig up a container/hose so I can run the engine with the tank off.  Will start playing with jetting again once I know the carbs are in sync.   A Triumph mechanic told me he has seen them out of sync from the factory so its worth doing.



I ordered the jets through Triumph dealer and don't know the source they used.  They were like $4 or $5 each if memory serves.   I also need to buy or rig up a little right angle screw driver so I can adjust those pilot screws with the carbs mounted and enigine running.   Its a tight fit and I have not seen a tool that will do the job other than the factory tool shown in the manual; which I expect costs a bit but there may be no other choice.      



I also want to try the timing advance too... but one thing at a time.  I'll post results if/when I learn anything.  



Scott