As you read this thread bear in mind it is intended to pertain to specifically 1983-1986 TT600s & 1984-1989 XT600s.



I am in the process of building a motor for my 86 XT600. I currently have an 85 TT600 motor with a bottom end going out and a good top end installed in the bike. I also have the XT's original motor with a good bottom end & a bad top end. I am thinking that I will use the good TT600 top end on the good XT600 bottom end. If I go this route I am trying to decide if I want to use the TT cam or the XT cam. If I don't go this route I will rebuild my XT top end & use the good XT bottom end. If I rebuild my XT top end then I am wondering if I should go with the TT cam or the XT cam. Either way I will be using the XT bottom end as it is good & because I want the lower first gear that XT transmissions have compared to the TT transmissions.

I have been trying to find out the differences in 83-86 TT600 vs 84-89 XT600 cams. I have searched the net & around this forum & all I have been able to find out is that the TT is supposed to be a more performance cam. I also read the the performance boost of the TT cam is in the lower rpms & there is a trade off of power loss in the upper rpms. I do not know if this is correct however. As far as I know it may all be a load of rubbish.

I have been trying to find out the differences in 83-86 TT600 vs 84-89 XT600 cylinders. All I can find out is that the XT has a cast iron cylinder & the TT has a Nikasil cylinder. As I understand it the Nikasil is a slicker surface that allows for higher rpms with lower engine temperatures due to decreased friction. What I am wondering though is what actual performance differences there are if any between the two cylinder linings.

I am also wondering if there are any carb differences between the XT & TT carbs besides jetting & needles. While I have been researching finding info on cams & cylinders on the TT & XT 00s I ran into some info that claimed the TT600 has a larger secondary carburetor throat. I know the TT & XT have different needles & jets but I am unsure of the throat diameters being different. I am wondering if anyone can shed some light onto whether these carbs have different throat bodies or if this too was just rubbish.

As far as the cam & cylinder choices I may choose I am considering all of the following:

XT cylinder with XT cam
XT cylinder with TT cam
TT cylinder with XT cam
TT cylinder with TT cam

Regardless of which cylinder & cam I choose I will be running the heavier XT rotor/flywheel & the XT ignition to run street legal lighting. I actually have the XT rotor, stator, pulse pickup in the TT motor that is what is currently installed in my XT at this moment. So I know that all these parts are compatible but what I am wondering is whether or not the heavier rotor & ignition choice is gonna have an effect on which cylinder & cam I should choose.

What I am hoping comes out in this thread is for someone that really knows these motors to offer the following:

1 A true & valid explanation of the physical differences of the two cams

2 What each cam provides in regards to performance

3 When the performance is higher for each cam in regards to rpm range

4 When the performance is lower for each cam in regards to rpm range

5 Besides Nikasil being a slicker surface what difference in performance is there between a Nikasil vs a cast Iron cylinder

6 As far as cylinder & cam choice when it comes to the performance of various options is one setup best for road, one set up best for dirt, one set up best for both?

7 Does the use of the XT's heavier rotor/flywheel &/or ignition have an effect on which cam & cylinder should be chosen?

8 Did the 84-89 XT600s & 83-86 TT600s have different sized carbs?

Even if you don't have all the answers on please share what you know. I would really appreciate any info that anyone has. No doubt if this thread gets to the truth in all this the info will invaluable for many people like myself trying to get all his sorted. Thanks.

I've been doing a bunch of parts swapping and comparing with building a hybrid motor and putting things in bikes/quads ,I've gotten used to Yamahas way of numbering. I can almost guarantee that the cam is the same because the middle group(actual part #) and the third ( variations/version) have the same number. The first 3 letters/numbers mostly only tell what vehicle the part is put in or model( this is still my best theory). I have physically compared quite a number parts like this and all so far have been the same. If the third series is different then it may or may not fit.

The heavier flywheel should work better for street no matter which cylinder is used to help smoothen out lugging and stop and go traffic. This is something I hope to test .

I don't think there will be much of a noticeable performance difference the plated and non plated liner. A slightly higher comp piston (maybe 10.5:1 not 11.5) will be a better option than to worry about liner.
Gearing is the same on both, all numbers are identical even the first series.
Go to this website and open 2 tabs with one the TT parts and the other XT and compare back and forth.

The carbs I believe is mostly jetting changes, I see the TT has bigger mains and pilot, needles are the same.

Ah finally some info that starts to make sense. What you are saying about the number series sounds legit.

I think you are right about this. I have heard others mention similar concepts. I didn't ride the TT I had long enough to really get a good feel for it but I do seem to remember it was jumpier then the XT when they both had their own fly wheels. Another bonus I hear to the heavier fly wheel is that it will carry more momentum for kick starting which allows more force to be created to spin the motor. I am guessing a lighter weight flywheel will spool up & down quicker as the the motor is revved up & down. The heavier flywheel would resist building momentum and loose less momentum when the throttle is adjusted. A heavier fly wheel will also hold speed better on rolling terrain with less throttle adjustment I would assume. As you say the heavier weight of the fly wheel "helps smooth" things out.

I hope this is the case. I am more concerned about smooth reliable day to day performance then I am in high performance. Sometimes high performance options can be a headache for day to day riding it seems. I am less concerned about performance & more concerned the the bike just runs good & and is easy for me to put together. I already seem to have a good Nikasil cylinder so if there is no reliability or specific performance characteristics that are lost by not using the XT cast iron cylinder then I will just go with the Nikasil cylinder for now.

The main reason I am concerning myself with the cams & cylinder liners is I want to be sure that the parts match for consistent performance. I have horsed around with some bike tunes that were half OEM/sport grade parts & half racing parts. Such tunes are always crap it seems as the OEM sport parts will be tuned for one shape of power band & the race parts will be tuned for another power band with the end result power band just not really good for anything because half the tune is focused on one rpm range & the other is for another rpm range. This is why I am trying to sort the parts out. Its not so much the max HP or something I am after. I just want everything to be in balance.

This is what is probably the case. Following your parts theory while the 3rd set of numbers is different between the carbs this could simply be due to the jet & needle differences I would think. Since I have both carbs I will measure them with a caliper whenever I have them off again. In all honestly while I have seen multiple references to the TTs having "hotter" cams and gearing differences I have only seen one mention of a difference in carb throat diameters & it was on a forum so ???

Now here I am still kinda wondering what is up & this is what is causing me to wonder. There are multiple mentions around the internet that have stated there is a difference in first gear between these transmissions. Several weeks ago I actually made a spread sheet comparing all of the transmission parts between the TT & the XT. Everything was the same according to how you describe the part numbers with the second set being the actual part. So after looking at the chart comparing the parts I began to wonder if people on the internet claiming first gear was different were comparing older & newer models of XT & TT. The newer XTs do have a higher primary gear as I understand it so maybe that is where all this talk is coming from.

Then a few weeks ago I was messing with the GearingCommander website. Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator

On the GearingComander site I noticed it showed two different 1st gear ratios for 80s TT & XT bikes. It showed 31/12 for an 80s XT600 first gear & 30 / 13 for all TT600 first gear. Below all my writing in this post are pics showing the gearing difference according to GearingCommander. When I saw this on the GearingCommander site I was like well maybe the gearing is different for 1st gear. Now I looked it up again tonight to grab the below pics & I noticed GearingCommander is also saying that the 5th gears between the two bikes are different also. But this can't possibly be right as the OEM part numbers for 5th gear & the 5th gear wheel are exactly the same for both XT600 & TT600 bikes. The OEM part numbers for the main axle which I assume holds first gear only match in the center numbers. So if you are right about the part number system then GearingComander has the wrong data plugged in. There is all this hearsay on the net, part numbers seem to match, and GearingCommander is showing different ratios. Its kind of a mess.

Below are the only part numbers that differ between 85 TT600 & XT600 transmissions. Everything else has exactly the same part numbers, including 5th gear & 5th wheel. The main axles sold with a complete set of gears or by themselves have differing first three digits & the main axle bearings have different second digits.

TT600 Main Axle complete with all parts 34K-17410-00-00
XT600 Main Axle complete with all parts 5Y1-17410-00-00

TT600 Main Axle by itself 5Y1-17411-00-00
XT600 Main Axle by itself 34L-17411-00-00

TT600 Main Axle Bearing 93306-30540-00
XT600 Main Axle Bearing 93306-20540-00

So I am just left wondering what is the truth in all this. Are the main axles different in there first gearing? Maybe all this first gears are different is partially coming from GearingCommander having the wrong data? If you are right about your analysis of the part numbers then the main axles & corresponding gearing would have to be the same though.

Until I have the parts in my hand to compare or some kind of known proof one way or the other I am just gonna let the gearing issue rest. Its kind of a moot point for me anyway as I am gonna build on the XT bottom end & have no intention of messing with the tranny just to find out what is up. If I ever disassemble both trannys I will count the gears.

Sorry about forgetting to add the website link to the oem parts place I use, meant to have it in my post to look at the part numbers. 1984 XT600L Yamaha Motorcycle Parts

The one problem with the plated TT cylinder is once it is worn, it is done. You can bore it out and have it replated, but they are never as good as the original factory, I think it has to do with oil penetrated into the walls and the plating then flakes easier. As long as it is within spec the TT should be good, they do wear a little longer than the non plated.

Anyway, since the gears are the same #'s and the bearing are different I think they just used a different bearing in the TT (but why?) so that corresponds back to the axle assembly # needing to be changed slightly, I would bet the axles are interchangeable. Gearing commanders # must be wrong or they are comparing the XT/TT550 and the 600's. Anyone have a factory TT service manual to see what the ratio truly are? Also I see it has '89 XT, it's possible the '88-'89 has changed there also, these years have several differences to the '84-'87 years.

EDIT: I see the bearing that has different numbers between the XT and TT are actually the same trade number, so the physical dimensions are the same, it is the seal or seals that was changed, maybe they used a bearing that had 1 seal and the XT had none or 2 ect... have to look into why it was changed.


I did see the '84XT part breakdown, there is 2 carb assembly numbers, 1 for 49 states(and the rest of the world), 1 for California(leaner jetting only diff., third series of numbers is changed to 01, it shows the third series change to the standard part.

Momentum is indeed the other reason for the heavier flywheel, and for kicking it would again be nice to know just how much a difference it makes.

Yah that boats.net sight is good. I like it because it shows all the other bikes & atvs that use a certain part. Its nice for cross referencing parts.

This all makes sense. I have read elsewhere that replating is never the same. I know from experience with welding that aluminum is a porous metal that will absorb oil & debris to some extant. Welding old used aluminum can be a bugger due to oil & dirt soaking into it over time.

I am glad you brought refurbishing these Nikasil cylinders up. Something I have been wondering is this; I understand why Nikasil can't be honed, obviously to do so ruins the plating. What I don't understand is why no one talks about just boring the Nikasil cylinders out & resleeving them with cast iron sleeves. Can this be done? I assume it can. I mean to say the cylinders between the XT & the TT only differ in that the XT has a cast iron sleeve & the TT is Nikasil coated aluminum barrel right? So can the TT cylinders just get bored out, sleeved with cast iron & essentially converted to a standard XT style cylinder?

The below pic is what the 1984 TT600 service manual says for gearing specs. Note that 2nd gear in this manual is saying 27/16 while the GearingComander is saying 27/17. I bet you are right. The GearingCommander has mistakes I believe.


I just did a little cross referencing of parts & I believe you are correct that there were some gearing changes during the 83-89 years. I have seen some transmission parts numbers for 83-89 XT & TT are the same, some transmission parts numbers for 83-85 XT & TT are the same, some transmission parts numbers for 86-89 XT & TT are the same, & some transmission parts numbers for 83-89 and even newer into the 1990s XT & TT are the same. When I have a moment I will compare out all the different parts & see what I can come up with for what went where when. Considering some parts between the 1983-1985 XT550s & XT600s differ with the 86-89 XT600s while the GearingCommander says 83-89 XT600s are all the same it is a safe bet that the GearingCommander has several errors.

Does anyone have the specs for gearing on the various XTs between 83-89?

All this sounds legit. I have read this via cross referencing parts & assumed all this to be correct.

I am not sure of the difference in kicking over the too fly wheels as I didn't have the my TT with a light weight fly wheel very long. The heavier fly wheel has to carry more force as it spins just cause of the physics of the whole scenario. When I had both fly wheels in my shop I weighed them. The 1985 TT fly wheel was 4lbs 8oz and the 1986 fly wheel was 6lbs 7.7oz. I don't have the TT fly wheel any more. I wish I did. I meant to measure its inner & outer diameters. I believe that while the inner diameter is the same between the two fly wheels the outer diameter is different. That is why if a TT or XT swap fly wheels the pulse pickup needs to be swapped too. It may have to due with something else though. When I swapped the fly wheel off my XT into my TT motor I swapped the stator & pulse pickup into my TT case & everything worked fine. I have read when the pulse pickups are not swapped things don't work. Maybe it has to due with some other aspect besides external width though I am not sure.

I just want to say thanks jjrider for helping get all this together. I don't always pay attention to member names on these forums. Today I just noticed we have been conversing on these topics across two forums & a couple different threads for over a month now. By far & large the info you have brought to these threads & other threads that I now realize you had a hand in with others folks have been a huge help. Thanks a lot for the help.

Instead of messing with boring and installing a new cast iron sleeve, just purchase an XT cylinder on eBay. Probably much cheaper, even if you need to bore it. Plenty of them out there...

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

As to parts numbering, it has been my experience that the first set of numbers are very significant. The remainder of the part number denote a series of a part, and explains the same numbering of the XT and TT front axle. I do believe they are different though, since you have both, are the front axle's exactly the same or is there some difference, like a way to pull the TT axle out?

In other words, if the first numbers are different, the part is unique. You have to go by the entire part number.

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

Ive done a bunch of parts comparing with the parts physically in my hands to double check and other checking into it. The first three numbers are mostly just the model that part is for or made for,( like 34l= '84xt600/motorcycle, 5lp=raptor atv,ect...) I've found that series has little to do with the actual part. It's the second series that is the specific part and design, the third 3 is any re-designs or updates ( this is where there can be some changes to the part), the fourth I'm not sure. I've probably confirmed this with about 20 parts that the first number are totally different but the 2nd series is indentical and the parts are the same .

Now this isn't fail proof or exact, but you would be surprised once you start to physically have the 2 parts in hand and make note of the numbers , how many parts are used across the model line, just the first number changes.

For instance, the oil pump on the '90 XT600 vs 2005 Raptor 660 atv
................................... 3AJ-13300-00-00 vs 5LP-13300-00-00
both of these parts are identical, I have both and measured them to confirm.


Many of these parts, like those jets, on Boats.net when you select the part number it shows a list of what models that part fits, and quite often it comes up with bikes , atv, scooter, snowmobiles , all across Yamaha's lineup ,using that part or could use it.

I'm really finding this out as I am putting the XT600 cylinder and top end on top of a 660 Raptor bottom, everything bolted right up, cam chain fits the 600 cam gear(same part #), the 600 piston fits the 660 con-rod( same stroke), many parts are the same # except the first series. Of course I haven't fired it up yet

I didn't know you mentioned the wire trick. At the UK site was the first I had heard of it. It seems like an okay temporary trick. It seems that it would be good to use if one was curious if a leaner jet would be worth purchasing, in a pinch on a tour up into the mountains & things get too rich or on a bike that doesn't get ridden much, ect.

Another part I ordered for my XT carbs is the newer pilot set screw from the 1990 & newer XT600. I am curious as how it will compare to the older screw.

I can't wait to see this project XT Top/Raptor bottom. Have you got a thread up yet with some pics of the project?

Good luck getting the Raptor carbs going too. I may do the Ninja or Raptor carb conversion after I play with the TK YDISs some more. After doing research on all these TT & XTs I am also wondering if the carbs off the newest XT660 or TT600 sold in Europe will work on the old motors. Another avenue I want to look into is some kind of throttle body fuel injection. A fuel injection conversion would probably be spendy but sure would be sweet.

THE newer 660 bikes are single carbs, which you can get a Grizzly 600 intake that reduces the two carb designed head into a single carb, but then you run into room with the shock. A person would need to have an offset intake so the carb sits a little crooked then the airbox boot could get to it.
I recently bid on but lost, a Raptor 700 EFI throttle body and harness, that would be a good one, especially with the 660 bottom, it has a few more sensor the efi uses. A person can sometimes get the whole system for $350-$400, maybe next year once I have all my projects settled in and get bored again

That secondary jet adaptor would be a good idea, but if these 350 or 225 jets do indeed fit it will provide many of the options one would need then. I wonder if the adjustable needles or the entire secondary slide would fit from there, if it has an adjustable needle.

I also bought a set of four Mikuni's from a Kawi street bike that are 32mm (IIRC), I got them for $45, will need to fab some throttle connections and mounts though. The Raptor carbs fit right on except the snout is another 4mm bigger dia. so the boots need to be ground bigger id or the carbs need to be machined smaller od. That's one of my biggest holdups, I've been trying to find another model/brand that has boots to fit the carbs and can be easily modded or bolt right up to the head. I hate to cut up $80 boots.

Ah bummer on the new XT660 carbs. I know of the troubles installing a single carb. I didn't realize the XT660s had a single carb.

Well the 350 has the other style of secondary jet like the 1990 & up XT600e carbs. So only the primary main jets can swap over to the older XT600s but not the secondary main jets. Maybe there is some other stuff that fits too. I am not sure.

The Raptor EFI sounds sweet. I saw it was a single throttle body though. To bad it can't be a dual body setup.

If the Ninja 250 carbs fit how about a Ninja 250 EFI conversion? Here is one Kawasaki Ninja 250r Fuel Injection Conversion Kit - Small Engine EFI Conversion kit | fuel injection kits I am not sure if this is the right kit that matches the carbs that fit the XT. What year of Ninja 250 carbs work for the XT carb conversion?

Not true , ALL XT / TT 350, ALL XT/TT 550 , 600, 660 up to 2003 all have TK double carbs , and are all very alike.

The "new" 660 engien in the XTR and XTX 660 from 2004-today and also used in the XTZ from 2008-today are single trothle body injection

As for jets and carbs the 2kf model XT 600 has a slitgly different, bigger tk 27 , the same that is used in the 660 tenere from 92-99 and the TT600 , also
the later TT 600 R also has a different one with a diferent jets

you could try ato get a more recent carb from a european model and maybe be easier to get jets for that

also some models in europe were power limited to local licence limitaitons , theses had different jetting also , if you can hget these you could just drill them out

also check the swiss spec bikes that had different carb setiting (generally leaner)