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...

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

I think I hear what you are saying. Is this what you mean?

The XT cylinders have cast iron liners. Even if worn the liner can usually be bored to the next piston size.

The TT cylinders are aluminum with a Nikasil spray on coating. In order to sleeve the cylinder it has to be bored out big time & have the sleeve installed.

Because of this it is more affordable & practical to simply get a used XT cylinder with a decent sleeve, bore the cylinder to match the next piston size up, done. No sleeve involved.

One other question I have about the Nikasil cylinders is can they just be bored out, skip the Nikasil coating, toss an oversized piston in, done? Or is the aluminum to soft to hold up on its own as a cylinder wall?

Its not so much that I am considering doing all these different methods. I just am curious of all the different methods that could be used to rebuild a top end.

You wouldn't make 10 miles before the Aluminum is ground into a pile of shavings, if it didn't seize before that. You'd have to bore it out and install a sleeve, which as Steve said, it would then be cheaper/easier to just get an XT cylinder with sleeve already there.

That is good to know. I was pretty sure that is how rebuilding aluminum cylinders went. Most of the projects I have done in the past were either cast iron cylinders or sleeved with cast iron. Any project I have done with aluminum cylinders was new enough to just go out and buy a new cylinder for when I needed to mess with them. Things are a little different when parts aren't exactly a phone call away for these old bikes.

After discovering that the TT motor I picked up was less rebuilt then I became a little paranoid over what other corners may have been cut. Its good to know tje cylinder had to have been taken care of properly one way or another. Now I am curious as to whether the top end on the TT motor is a cast iron sleeved cylinder or a replated Nikasil cylinder. The previous owner said he paid a lot of money to have the cylinder "returned to OEM spec." Maybe he had it replated. Funny thing is after coming to know about the TT and XT cylinders I would prefer to find a standard XT cylinder with a liner when I pull the top end off to put it onto the XT bottom end when I get around to it. Then I don't have to worry about replated Nikasil lining flaking off.

I really don't trust the replating to be done right. I sent a KX500 cylinder to US Chrome as it had suffered a seizure and damaged the bore. At their suggestion a Sent a new Wiseco standard piston as they said they would just skim bore then re-plate to original bore diameter. When we got it back and installed it, the piston rattled horribly. We pulled apart and check clearance (should have done that first but trusted them). Wiseco says to set clearance to .004" 4 thousandths inch). The clearance as measured by a feeler gauge was over 6 thousandths. I sent it back to them. They tried to tell me the piston must have shrunk as the bore was perfect. I don't believe that. They said they could add a coating to the piston to make up the difference. I doubted that would last either but what could I do. We got it back and it did measure 4 thousandths. We put it together and it still rattled, maybe not quite a much.

I know forged pistons rattle a bit more than cast pistons but how much is too much? I now know that I should have had them bore 1st over, plate to fit the 1st over piston...

US Chrome never again......

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

Tried to tell you the piston shrunk? I have never heard of anything like that happening to a piston or any other metal object outside of science fiction. Obviously metal can expand when hot & shrink when cold but at room temp when a piston is measured or a cylinder is worked on ect they simply exist & will measure consistently. Last time I checked that is how the science of metal works.

Can pistons actually shrink somehow?

Ya , if you stick it in liquid nitrogen and freeze it to -350ish F , It was just a typical company knowing they screwed up but trying to blame it on something else so they could save ego.

I have been doing research tracking down jets that will work in the TK YDIS Y27PV carbs found on the pre 1990 XT600s. I used your ideas on part numbers & I was able to come up with a large number of jet options that will fit for a primary main jet in these carbs. Most of these jets are no longer in production but can still be found used. Unfortunately I was only able to find 4 possible jets for the secondary carb main jet none of which are in production of course.


I also may have found some insight on the rumor that the TT600s have larger diameter carbs then XT600s. Here is what I found. 1980s XT600s & TT600s had 27mm carbs. In the early 1990s XTs went up to 28mm carbs. XT600s kept these 28mm carbs till XT600s went out of production in 2003. TT600s on the other hand received 30mm carbs starting in the mid to late 1990s. By 1998 I am pretty sure that the TT600s definitely had 30mm carbs. So if someone was comparing these bikes the TT600 did have a larger carb in the later models. XT600s became XT660s & then they were given 44mm carbs but the XT600s never had carbs larger then 27mm. So depending on the year TT600s can have larger carbs then XT600s.


Here are the results of my researching carb parts for the Teikei Y26PV & Y27PV carburetors. Part numbers in bold are currently available new from any Yamaha parts distributor. Parts that are italicized are no longer in production. Some of the part numbers in the series were never made. These I noted as "No record of..." A few of the jets may have been made but if so they are so limited that they only appear in very obscure references. The out of date part numbers can still be used for searches on ebay & what not. Obviously some of these jets are too small for use with a XT600. I included them though as if these jets could be found they would make good candidates for drilling to size especially if they are found for a good price. While I compiled the list I watched for which motorcycles these jets were sold for. I saw several models that crossed over through the jet selection. Because of this I am most positive they will all have the same shape, thread, ect. that will allow them to fit in XT600 Y26PV & Y27PV carburetors even though the jets may have originally been sold for other bikes/snowmobiles/carbs ect.



Pilot Air Screws for Teikei Y27PV & Y26PV Carburetors

50M-14105-00 1989 & older XT600s & 1983-1986 TT600s

51Y-14105-00 1990 & newer XT600s


Pilot Jets for Teikei Y27PV or Y26PV Carburetors

#40 43F-14342-20

#42 43F-14342-21

#46 43F-14342-23

#48 43F-14342-24

#50 43F-14342-25

#52 43F-14342-26

#54 43F-14342-27


Primary Main Jets for Teikei Y27PV or Y26PV Carburetors

#66 288-14343-33

#68 288-14343-34

#70 288-14343-35

#72 288-14343-36

#74 288-14343-37

#76 288-14343-38

#78 288-14343-39

#80 288-14343-40

#82 288-14343-41

#84 288-14343-42

#86 288-14343-43

#88 288-14343-44

#90 288-14343-45

#92 288-14343-46

#94 288-14343-47

#96 288-14343-48

#98 288-14343-49

#100 288-14343-50

#102 288-14343-51

#104 288-14343-52

#106 288-14343-53

#108 288-14343-54

#110 288-14343-55

#112 288-14343-56

#114 288-14343-57

#116 288-14343-58

#118 288-14343-59

#120 288-14343-60

#122 288-14343-61

#124 288-14343-62

#125 288-14343-63

#128 288-14343-64

#130 288-14343-65

#132.5 288-14343-66

#134 288-14343-67

#135 288-14343-68

#138 288-14343-69

#140 288-14343-70

No record of 288-14343-71 or 288-14343-72

#146 288-14343-73

#148 288-14343-74

#150 288-14343-75

#152 288-14343-76

#155 288-14343-77

#156 288-14343-78

No record of 288-14343-79

#160 288-14343-80

No record of 288-14343-82

#166 288-14343-83

No record of 288-14343-84

#170 288-14343-85

No record of 288-14343-86 or 288-14343-87

#176 288-14343-88

#180 288-14343-90


Pre-1990 XT600 Secondary Main Jets for Teikei Y27PV Carburetors

#120 5Y1-14343-60

#125 5Y1-14343-63

#130 5Y1-14343-65

#136 5Y1-14343-68


1990 & Newer XT600 Secondary Main Jets for Teikei Y26PV Carburetors

#80 30X-14343-40

No Record of 30X-14343-41

#84 30X-14343-42

#86 30X-14343-43

#88 30X-14343-44

#92 30X-14343-45

No Record of 30X-14343-46

#94 30X-14343-47 (Maybe it exists)

#96 30X-14343-48

No Record of 30X-14343-49

#100 30X-14343-50

#102 30X-14343-51

#104 30X-14343-52

#106 30X-14343-53

#108 30X-14343-54

#110 30X-14343-55

No Record of 30X-14343-56 or 30X-14343-57

#116 30X-14343-58

#118 30X-14343-59 (Maybe it exists)

#120 30X-14343-60

No Record of 30X-14343-61 or 30X-14343-62

#125 30X-14343-63

No Record of 30X-14343-64

#130 30X-14343-65

No Record of 30X-14343-66 or 30X-14343-67

#136 30X-14343-68

No Record of 30X-14343-69 or 30X-14343-70 or 30X-14343-71 or 30X-14343-72

#145 30X-14343-73

No Record of 30X-14343-74 or 30X-14343-75 or 30X-14343-76 or 30X-14343-77

#155 30X-14343-78

No Record of 30X-14343-79

#160 30X-14343-80