'98 Tiger jerky acceleration - please help !

[Mike_PL]

Hi all !

I've a problem with my 98 Tiger. after the (exceptionally long) winter I noticed that the bike stalls over 4k rpm. I had it partly serviced (e.g. fuel drained from bowls) and the mechanic changed the pilot screw setting to 3.5 turns out - Keihin, main 98, pilot 38.

Valve clearance not checked, nor the spark plugs.

It feels a little better now, yet the engine revs very reluctantly as if with resistance and jerks. Once over 6000 rpm power kicks in all right, but the mid range really sucks.

I can't understand why he changed the pilot. isn't it the jet needle that is responsible for mid range ??

What would be your guess?
Should I simply clean the carbs and air-blow the jets?

BTW, I went thru other posts on settings. could you confirm the main jet in the picture is the one when you are talking about rejetting the stock carbs (I mean its shape & size). Is ths how it looks like ???

[rf9rider]

First and easiest thing to check is that you have the cap fitted to one of the airboxes.
Your carb settings look a little strange compared to stock to stock though.

[rf9rider]

Quote from Mustang;

if you have keihins they came lean from the factory , like seriously lean

factory settings were
98 main jets
#40 pilot jets
non adjustable needles and the pilot screws were basically almost closed

what works well with keihins is
105 main jets
shim the needles up with some washers that are .030-.050 of an inch thick
and set the pilot screws to around 2 turns out
big improvement

on either setup it assuming that only one snorkel is open on the airbox , there should be a blanking cap on the right hand snorkel.

if not it will be sucking too much air will need some serious increase in mains and fuel mileage will suffer

[Mike_PL]

so there should be one cap on, an the other one not.

I can't see the connection between this and the jerky engine play...  

Are you saying I'm getting too much air in relation to fuel ?

BTW, my millage is now slightly above 55mgp (6.2l/100km)
is this too good and I need more fuel indeed ?

[nightrunner]

The same thing happened to me when I brought my 98 out of hibernation several years ago.   I fought with the carbs for weeks.  It would run fine at high RPM but would not idle, and would miss and sputter at low and mid-range.  It was the damn coils.  There is much written on this forum about the coils.   If its not the coils, they will fail soon enough anyway.  Two ways to go.  Most folks like the direct swap of the Nology coils.  Search here for coil threads or Google Nology.    The second, and less costly, way is to pick up a set of 4 on-the-plug coils on ebay from a TT600 and extend the stock coil wires over to the plugs.  This gets rid of to old coils and the plug wires so there is less to fail.  Yes, the coil itself is inside the spark plug boot.  A used set will cost you maybe $30 plus some wire and connectors.

The other possibility is the carbs are dirty.  It seems that some steamers need a carb cleaning every spring.  So yes, you could yank the carbs and give them a good cleaning.  Jet should be removed so you can see through the orifice.  If you've never pulled the carbs it is a rite of passage in the steamer club, and a royal pain.   Put some wheel bearing grease on the rubber boots and reassembly will be a snap.   Others have recommended that you undo the throttle cable at the handlebar since its very hard to disconnect it at the carb.   I support the carbs to the crash bar and work on them there so the throttle cable stays attached.  Lots of threads here on the carb cleaning.  

Good luck

[nightrunner]

Quote from Mustang;

if you have keihins they came lean from the factory , like seriously lean

factory settings were
98 main jets
#40 pilot jets
non adjustable needles and the pilot screws were basically almost closed

what works well with keihins is
105 main jets
shim the needles up with some washers that are .030-.050 of an inch thick

I suspect this may be a typo.  When I bought the 100's and 40's for my 98, they told me those jets only came in odd numbers.  And 105 (or 104 or 106) would be a huge huge step up for a jet.  It might be suitable if you have aftermarket exhaust and the K&N pod air filters.  Usually if you are lean at wide-open-throttle then one step up does the trick.  Read about carbs here:

http://hondanighthawks.net/carb14.htm

And here is more detail on rejetting
http://tigertriple.com/forum/viewtopic. ... highlight=

[Mustang]

yes the mains look like your pic

get some #40 pilot jets in there at least and at the minimum 100 mains but I would go with 105's  shimming the needles with a flat washer helps the mid range tremendously  pilot air screws at 2  to 2 1/4 turns will put you right on the money with the carbs  and keep the rubber blanking cap on either the left or right snorkel opening .

you could well have coils going .........thats exactly how mine failed only ran on two cylinders up to about 4500 then the third cylinder(coil ) would come back alive and run like a freight train to redline ........


and when the gill coils are going you will swear on a stack of bibles that you have carb problems but it is them crappy Gill coils .

[nightrunner]

I suspect this may be a typo.  When I bought the 100's and 40's for my 98, they told me those jets only came in odd numbers.

Sorry I meant I was told they only come in EVEN numbers.  Stock was 98, next available size was 100, etc.

[Mustang]

I suspect this may be a typo.  When I bought the 100's and 40's for my 98, they told me those jets only came in odd numbers.

Sorry I meant I was told they only come in EVEN numbers.  Stock was 98, next available size was 100, etc.

they told you wrong

you can even get jets in half sizes
ie. a 107.5

and why would you presume that a 36mm Keihin would not like 105 mains if a stock Mikuni that is 36mm runs the balls on 105 mains  ??? Just curious

[Mike_PL]

The same thing happened to me when I brought my 98 out of hibernation several years ago.   I fought with the carbs for weeks.  It would run fine at high RPM but would not idle, and would miss and sputter at low and mid-range.  It was the damn coils.  There is much written on this forum about the coils.   If its not the coils, they will fail soon enough anyway.  Two ways to go.  Most folks like the direct swap of the Nology coils.  Search here for coil threads or Google Nology.    The second, and less costly, way is to pick up a set of 4 on-the-plug coils on ebay from a TT600 and extend the stock coil wires over to the plugs.  This gets rid of to old coils and the plug wires so there is less to fail.  Yes, the coil itself is inside the spark plug boot.  A used set will cost you maybe $30 plus some wire and connectors.... Good luck

Nightrunner thanks a lot for your insight.
are those u r talking about ?
1. http://cgi.ebay.com/ebaymotors/2002-TRI ... 5d28834074
2. http://www.nology.com/hot.html

Mustang thanks for confirming and help.

I'll report back to you after the work is done. Now I know where to start from.

One more question: could unadjusted valves have any relation with the symptoms in my bike? to the tiniest extent even ?

[JetdocX]

Probably not the valves.  If the valves were too tight you would have a helluva time starting the beast.

How old is the gas in the tank?  Were the foat bowls full all winter long?

[Mike_PL]

...How old is the gas in the tank?  Were the foat bowls full all winter long?

the old gas is all gone. poured a bucket of new. and the bowls were full, emptied at the servicing facility.

but I guess I'll have to clean deeper myself, won't I ?

[nightrunner]

Nightrunner thanks a lot for your insight.
are those u r talking about ?
1. http://cgi.ebay.com/ebaymotors/2002-TRI ... 5d28834074
2. http://www.nology.com/hot.html

Mustang thanks for confirming and help.

I'll report back to you after the work is done. Now I know where to start from.

One more question: could unadjusted valves have any relation with the symptoms in my bike? to the tiniest extent even ?

Yup those skinny little sticks are the ones.  You will also need some tiny little female spade (or 'flag') connectors.  The standard 1/4" for automotive are too large.  They make smaller ones, like 1/8" but you have to go to an electronics store to find them.  Or if you are lucky you can find the connectors off the TT600 to go with the coils.  there are only two terminals in each coil and the tiny spade connectors will fit on them.  Other than that its just extension wore for where the stock coils mount.  

Or the Nologys are a direct bolt in.  I and a few others here went with the TT600 but most of the folks here have done the Nologys.

[nightrunner]

they told you wrong

you can even get jets in half sizes
ie. a 107.5

and why would you presume that a 36mm Keihin would not like 105 mains if a stock Mikuni that is 36mm runs the balls on 105 mains  ??? Just curious

Apparently I misunderstood when I bought them.  Keihin sizes listed here:

http://www.keihin-us.com/list.htm

Looks like it does go 98, 100, 102, and 105, and on.  

From 98 stock to 105 is a very big jump IMHO without air filter or exhaust mods.   With a K&N filter, that is a different story.

I know half sizes exist but that does not mean that every half size (or even whole number size) is available.  If my mains are 98, I cannot get a 98.5......unless I drill it myself.

[harre]

Even though my Steamer 98 (Keihin) runs really well and starts easily, I have noticed the bog at around 4000-5000 rpm and is considering a re-jetting. My main concern is that I want the same or better mileage (gas price in Sweden is today $6,4 per gallon). Now I get between 0,45 and 0,5 litres per 10 km (corresponding to 52-47 mpg (US)). Maybe this is difficult to improve on since it is pretty low. What would be the optimal Keihin setup? I surely would like a snappier gas response. I have an K&N air filter, foam pre-filters in the snorkels (one capped) and TT600 coils. Apparently switching to 100 or 102 mains and raising the needles may do the trick.