slip on with stock motor

[wildncrazyed]

I installed a DG slip on and removed the airbox cover and put a Uni filter on -- stock carb air screw readjusted -- Nice sound , but no noticeable power increase -- have other stock trx 90 to compare with ... I see the link to powroll and have read Jetting suggestion ... Looking for more punch out of the hole ... Nothing so far -- I put a performance CDI on -- same effect = Nothing changed . I cut the pink wire and Yes it is faster in 4th gear . I am fixing to change the Main Jet and Raise the Needle ... It currently runs,starts and idles OK now -- What main size ? 88 and needle ? 4th clip --- Will I or should I see some take off improvement ? Have a R4S mini slip on for other quad , but currently using stock quad for comparison purposes . Both quads were equal derestricted stock quads to start with...98 and 96mdl . Both drag raced evenly until the pink wire was cut . I can only hope that rejetting will allow the quad with the ; Pipe , Open airbox , Uni filter and CDI to show some Power Gain ! I feel like I have wasted time and money . Any advice as to what jetting and improved power results should be expected ?

[wildncrazyed]

I noticed instructions for R4S pipe suggest ... raise needle 1 clip position and pipe requires 1 or 2 sizes larger main jet = #82 or #85 . I hate that you have to remove carb bowl to change main jet . This means more time and effort to try several different sizes until a "just before rich setting is found" ... The DG disc style slip on is what I want to start with because of flow tuneabiliity , and it has 12 discs as received new . So I have to wait until correct main jet is found and then I can start removing discs to see what effect applying back pressure will have ? ... I was hoping someone has some previous experience and could share main size suggestions ? Also , if I am going to be looking for power that may or may not ever be found with just a slip on , filter and airbox lid removed ... I will find a best combination , but have no idea of what to expect for moneys spent verses effort and results . The children like the sound , however I'll be happy if power is gained . Powroll sayes #88 for below 96cc engines which is probably erring slight rich ... so anybody agree starting with #85 ? I kinda want to hit it rich first try and drop size once to "just right" and not test next smaller ; due to carb accessibility . I'll also compare stock vs. mod CDI !

[miniquaddad90]

most cdi boxes dont do a thing other than alter rev limit. The big gun cdi box will actually loose some HP compaired to stock. When we started our TRX90 ventures years ago, I did the same as you. Bought a DG oval slip-on, uni filter, etc... Get your jetting correct and you'll end up with a small minimal gain with a nice tone. To really wake these up, I would get a full exhaust-P.C., FMF, Big Gun, Yoshi, etc.... Make sure you dont buy a big bore pipe, you'll loose more than you gain. Full pipe, uni, cam, perfect jetting will be a nice improvement. After that look at higher compression and/or a big bore kit. You can easily get 10-15hp out of these if youre will to spend the $$

I think we ran a 85 or 88 main jet with our DG slip-on, uni, no lid, but that was about 5 years ago. Should be a good starting point. Also try going up to a 14 tooth frt sprocket or 48t rear, it will pull it with no problem

[wildncrazyed]

I appreciate the help !!! Hoping after finding the correct main size , there will be some kind of power gain in "off the line 1st , 2nd , acceleration , but so far it's not looking good with just a slip on etc... I didn't known to get the full system ! The cam and compression suggestion sounds great ! Any advice on a torque (Bottom-Mid cam ?) Which one and Where ? I like to add parts and check results as I go . Looking for acceleration/pull power . I was hoping the engine would respond better without re engineering and a lot of costly alternative aftermarket parts ... I'll be happy with 2 to 3 hp increase and enough torque to pull a higher sprocket ratio . Currently with just these parts there is NO power increase at all , however , the sound makes the children think they're going faster !... I've decided to start with the #85 main first

[miniquaddad90]

Check out the cams at DRATV . com, I dont think you will achive a 3hp gain till you raise the compression and/or bore size, just my opinion. Get the jetting right throw an inexpesive dratv cam and a 14t sprocket and I think you will be happy with the results. The sprocket wont help much for "off the line" power but will make it more rideable and faster overall. The 13t just seems to rev out too fast. These motors fully built will pull a 16/48 combo all day long.... Even stock motors seem to pull the 14t well in my opinion

[3inthedirt]

Are there any other modifications required for adding the DRATV cam? We have the slip-on, a uni and works shocks (obviously not related to the motor) and have re-jetted. Do we need any further jetting or larger carb to deal with the cam? Does the stock cam gear for the chain apply to this cam without modification?

thanks

[airmobile101]

I wonder about the cam also. Will it give a little more arse with just a stock engine with full exhaust? I'm getting ready to start building this 90,but I'm still up in the air about a big bore.

[miniquaddad90]

IMO Going with cam, full pipe, correct jetting is a decent improvement but not night & day. Kinda like adding a full exhaust to a larger quad-400ex, etc... Adds some good useable power across the power band. Keep in mind it's been 3+ years since we ran a silimar set up.

Now add some high compression and/or big bore, good porting and/or big valve head and it would be like going from a xr80 to a cr80

The only downfall of the big bore/big valve kits is getting the intake/carb set up to clear starters on the newer ones (depending on what carb/intake you want to run), retaining air box if needed, and getting these little boogers jetted perfect with the larger carbs. Once you get a good set up, spend an hour on a dyno and fine tune the jetting, well worth the $100 we spent @ dyno shop. I thought I had it real close, ran good, cold started kinda fair, fast and pulled hard.... BOY was I WRONG, it made good HP #'s but was still able to gain another 3hp by getting the jetting perfect. Starts way easier and runs perfect all day everyday!

Good luck fellas!

[wildncrazyed]

I tried a #85 main with the needle raised (lowered clip 1 position)... I personally felt improvment in throttle response when lifting front end during wheelies . I did not get a chance to let the children drag race against the stock quad . May consider keeping stock piston and later" Sanding Head and installing Cam ". Not sure which cam to use ? and how much to lower head ? . Ran out of time to install and test other jet sizes . I noticed some exhaust smoke (very slight) when child REEMED out rpms too much before shifting , but know this is normal because I have seen this before . These are older quads with little wear when we got them. The air screw adjustment was checked several times until a area of about 1/4 to 1/2 either way was found . Then more detailed tuning air / idle for quick throttle response . I haven't counted to verify exact turns , but I have removed most of the delay during quick stabs from idle . I can now tell there is a tiny air screw sweet spot 1/8 turn + - either way with a certain idle for best response , but it took some time to identify . Just installing a slip on without carb changes is a mistake ! It will require more fuel and the improvement is very little ! Should consider cam , compression or something else that will actually put torque in the engine .

[miniquaddad90]

DONT SAND THE HEAD!!! Find a machinest and remove Im guessing here .005"-.010". Prob could go .030" but with a high lift cam you may have some contact (valve to piston), not sure... When in doubt clay check it before you run it. (playdoh works too :huh )

[airmobile101]

Doesn't DRATV sell the thinner cylinder gasket? That would bump up compression right there!

[miniquaddad90]

Originally posted by airmobile101
Doesn't DRATV sell the thinner cylinder gasket? That would bump up compression right there!

YEPPERS! Forgot about those. Hey while the head is off open up the "bowl" area around the valves and port match the intake to the head and intake to carb

[airmobile101]

Originally posted by miniquaddad90
YEPPERS! Forgot about those. Hey while the head is off open up the "bowl" area around the valves and port match the intake to the head and intake to carb
Yea...... I'll bust out the dremel ASAP! LOL

[miniquaddad90]

Originally posted by airmobile101
Yea...... I'll bust out the dremel ASAP! LOL

Im gonna start charging for the free help then double it when sarcasm is included :macho LOL

[airmobile101]

Originally posted by miniquaddad90
Im gonna start charging for the free help then double it when sarcasm is included :macho LOL
hahahaha! I did it to my z400. And you thought I was being sarcastic! lol:D

[wildncrazyed]

I hate it but your absolutely right ... There is not much to get out of a stock engine , without taking it apart !!! I'm very glad you gentlemen gave me a heads up on NOT to sand and better to use a thinner gasket . By the way is that a thinner head gasket or thinner cyl jug base gasket ??--- What is the desired deck height ??--- Oh Yeah ; kinda educate me on the "clay , play doo" use ?? Not sure how to check or what to check ?? --- noticed better (quieter sound) & throttle response with the airbox lid on --- The back yard was the Labor Day 500 Dust Bowl --- everyone immediately knew which one felt stronger , and complained about the stock quad . Neighboring children brought there parents to show them what they wanted for Christmas ! We shared the fun , and both quads were run for 5 hrs solid ! I'm glad it's over !

[wildncrazyed]

Just a thought ; At a quarter a lap I'd could have made enough to mod both quads with kits ! Even the adults had brown dust muzzles !

[airmobile101]

Originally posted by wildncrazyed
I hate it but your absolutely right ... There is not much to get out of a stock engine , without taking it apart !!! I'm very glad you gentlemen gave me a heads up on NOT to sand and better to use a thinner gasket . By the way is that a thinner head gasket or thinner cyl jug base gasket ??--- What is the desired deck height ??--- Oh Yeah ; kinda educate me on the "clay , play doo" use ?? Not sure how to check or what to check ?? --- noticed better (quieter sound) & throttle response with the airbox lid on --- The back yard was the Labor Day 500 Dust Bowl --- everyone immediately knew which one felt stronger , and complained about the stock quad . Neighboring children brought there parents to show them what they wanted for Christmas ! We shared the fun , and both quads were run for 5 hrs solid ! I'm glad it's over !
Its a thinner base gasket. I didn't even run a base gasket on our old KFX50 that had a big bore kit. I just slapped some Permatex gasket maker on it,but I doubt you would want to try that on a TRX90. I never used playdo either, I just assembled the engine and hand turned the flywheel to see if I felt binding. I have used a piece of solder before. Kinda the same principle of checking the squish. Just stick a piece of solder in the spark plug hole and angle it towards a valve and turn the engine flywheel by hand.

[miniquaddad90]

Base gaskets are paper thin and dont know of a thinner base gasket out there and if there was, what are you really saving? .5mm if that after it's torqued. DRAVT offers a 1mm headgasket which is about half the thickness of O.E. style gaskets. If Im not mistaken, the factory honda head gasket is 3 layers. I've head from sum pitbike guys that you and seperate the gasket and remove the middle layer for a small bump in compression.

The solder trick is cool, never thought of that!

When you increase comperssion by changing piston or milling head, it would be a good idea to make sure that the new parts or set-up has the needed clearance inside the motor especially if running a high lift cam also. You could assemble the top end, put a small "glob" of playdoh or clay in valve pockets. Rotate engine over by hand, remove head and see what the thickness is at the valve to piston. Also check piston to head. You will generally need .050-.080" of clearance to allow for heat expansion. The solder would work great if you are positive pistion to head clearance is good.


My advise, get a cam and see if your happy with the results. If not, set up to a big bore kit. get something like a TB 114cc kit with big valve head (buy from Tbolt racing :) vince is a good guy) or a "privateer racing" 115cc kit from CHP. Kits will set you back 300-375 plus you will need a bigger carb. I can shed some light on a perfect carb for either kit. One that you can retain airbox and stock intake, after porting that is, eazy combo to install versus intake adaptors, custom air box boot,etc... just to use the Mikuni VM26. The Mikuni is great just too much micky mousing for my liking

[wildncrazyed]

I found "Beatrice--DRATV" ; Wow there are a lot of choices in head and base gaskets . Guess I need to know what thickness stock (base & head gaskets) are ? --- and some advice as to which cam and whether make changes to base or head gasket ? Wish they had a chart to know how much compression is changed per measurement --- This is where the reliability and longevity advice can only be answered by someone who has experience !!!--- I see the cyl kits , cams , gaskets and recognize there are many combinations . I also see there isn't a simplified ; Low , Med , High choice with explainations . It's like buying a slip on when I should have bought a full system ...I want more torque and hp without having to over rev & overheat the engine ... Children and adults are riding these quads non stop for hours at a time ... These engines stock do not come alive with simple bolt ons (slip on , jetting , rev box & sprocket changes) : when compared to bolt on results from 400 EX 's ... TRX 90 's require internal mods ! --- I probably need to put a thinner base gasket (size ?)and clean out head ports to match , maybe fresh valve seals and lap valves combined with cam (which one ?) . This is unknown territory and any suggestions are welcomed !

[airmobile101]

Originally posted by wildncrazyed
I found "Beatrice--DRATV" ; Wow there are a lot of choices in head and base gaskets . Guess I need to know what thickness stock (base & head gaskets) are ? --- and some advice as to which cam and whether make changes to base or head gasket ? Wish they had a chart to know how much compression is changed per measurement --- This is where the reliability and longevity advice can only be answered by someone who has experience !!!--- I see the cyl kits , cams , gaskets and recognize there are many combinations . I also see there isn't a simplified ; Low , Med , High choice with explainations . It's like buying a slip on when I should have bought a full system ...I want more torque and hp without having to over rev & overheat the engine ... Children and adults are riding these quads non stop for hours at a time ... These engines stock do not come alive with simple bolt ons (slip on , jetting , rev box & sprocket changes) : when compared to bolt on results from 400 EX 's ... TRX 90 's require internal mods ! --- I probably need to put a thinner base gasket (size ?)and clean out head ports to match , maybe fresh valve seals and lap valves combined with cam (which one ?) . This is unknown territory and any suggestions are welcomed !
lol, Yea.......... I have a OLD 70 DOME!!!!!! Or I have a new 70 dome!!! WTF!!!!! It can be confusing for sure!

[miniquaddad90]

Originally posted by wildncrazyed
I found "Beatrice--DRATV" ; Wow there are a lot of choices in head and base gaskets . Guess I need to know what thickness stock (base & head gaskets) are ? --- and some advice as to which cam and whether make changes to base or head gasket ? Wish they had a chart to know how much compression is changed per measurement --- This is where the reliability and longevity advice can only be answered by someone who has experience !!!--- I see the cyl kits , cams , gaskets and recognize there are many combinations . I also see there isn't a simplified ; Low , Med , High choice with explainations . It's like buying a slip on when I should have bought a full system ...I want more torque and hp without having to over rev & overheat the engine ... Children and adults are riding these quads non stop for hours at a time ... These engines stock do not come alive with simple bolt ons (slip on , jetting , rev box & sprocket changes) : when compared to bolt on results from 400 EX 's ... TRX 90 's require internal mods ! --- I probably need to put a thinner base gasket (size ?)and clean out head ports to match , maybe fresh valve seals and lap valves combined with cam (which one ?) . This is unknown territory and any suggestions are welcomed !

Base gasket change is NOT needed!! Get the thinnest cooper head gasket offered and you will gain a small bump in compression. As to how much, couldnt tell you exactly, prob still way under 10:1. BTW- Even @ 12:1 93 octane will do just fine. Stock head gaskets after torqued are about .040" or 1mm. If youre gonna take the head off, clean up the bowls under the valve. You will notice the portion to the inside of the head kinda cuts off flow to the entire valve. I will try and post a pic of one of our ported heads for you. I would agree on the new valve seals and if it was me I would do a new timing chain and tensioner spring (both available @ DRATV) at the same time. As far as cam choise the TBQ cam would be good for your set up or go with the Z40 if you ever have plans on a 114cc kit. If not the TBQ is a much better "all around" cam.

[miniquaddad90]

Originally posted by airmobile101
lol, Yea.......... I have a OLD 70 DOME!!!!!! Or I have a new 70 dome!!! WTF!!!!! It can be confusing for sure!

:D All TRX90's have the "new 70 dome"

[wildncrazyed]

Excellent , I just read your reply after posting ... I'm going to have to put you on the Christmas Ham List ! Your saving me before I even make mistakes . I might as well say recomend a good overall cam ... I didn't see any duration specs or power descriptions on the cams I've looked at ? I know quads really need to have torque for the weight . However they need power just as well . Guess I'm saying ; are there any TRX 90 quad specific "overall power/torque" cams ?... not the top end race cams that are for bikes . I think that is what some sellers have sold under the premise quote "will fit TRX 90" . Sometimes I have wanted to say ; "you lie to your friends and I'll lie to mine , but let's not lie to each other"... recently I asked a seller exactly what kind of cam is it ?... They replied : "it's a good overall cam (not top end race only) ". Basically repeating what I described and unable to give any facts as to the parts lift , duration or mfg .

[wildncrazyed]

Make that Christmas Ham with bottle of Wine !! Thanks for advice !

[miniquaddad90]

Originally posted by wildncrazyed
Make that Christmas Ham with bottle of Wine !! Thanks for advice !

I prefer Jack or Crown :eek2: LOL

The TBQ would be the best "all around" cam for the dollar and application. At $30 or $40 you cant go wrong.

I spent $200 on a Powroll cam but in all honesty have had better luck with some of the "import" cams for under $100 for our application.

Just about every cam out there will work on trx90, crf50, crf70's... with that said you will not find a "trx90 only" cams. They all use the same principals and basic designs so in the end all of the above respond about the same with modifications. The larger the lift and longer the duration the more of a mid-top end cam you will have. Here is a link on cam specs, dont get lost in all of the figures. TRX90's use the ABxx 12V listed on chart.

http://www.daikitana.com/Techinfo/Camshafts/

[swamp]

Just send us the motor and we will get u where u want to be...

something like the pink one

http://www.youtube.com/watch?v=dSBqctPznXA

[3inthedirt]

Does anyone see an issue with the following:

Our 90 already has a Uni filter and an FMF slip-on ( I realize a full system would have been better but this is a fun quad, not a race quad. I'm not going to spend the money for a full system at this point). The jets have been increased for these mods.

I want to add the DRATV cam, copper head gasket and 14-tooth countershaft sprocket. Do you think I need to rejet again?

[miniquaddad90]

Originally posted by 3inthedirt
Does anyone see an issue with the following:

Our 90 already has a Uni filter and an FMF slip-on ( I realize a full system would have been better but this is a fun quad, not a race quad. I'm not going to spend the money for a full system at this point). The jets have been increased for these mods.

I want to add the DRATV cam, copper head gasket and 14-tooth countershaft sprocket. Do you think I need to rejet again?

Prob not but possibly 1 size larger main just to compinsate for the additional valve lift and longer duration. I would try it as is 1st then go from there.

[3inthedirt]

thanks

[airmobile101]

Originally posted by 3inthedirt
Does anyone see an issue with the following:

Our 90 already has a Uni filter and an FMF slip-on ( I realize a full system would have been better but this is a fun quad, not a race quad. I'm not going to spend the money for a full system at this point). The jets have been increased for these mods.

I want to add the DRATV cam, copper head gasket and 14-tooth countershaft sprocket. Do you think I need to rejet again?
Never re-jet for cams. Just throw it in there and let her rip.

[wildncrazyed]

I finally compared the DG slip on with the R4 slip on and can only say the tone and slight throttle response difference is noticed . The DG sounds 'pop-pop' , louder at top rpm and quieter at low rpm . The R4 is 'nice deep smooth' sound and for some reason throttle response is better at low rpm punch . The main jet is slightly rich using a #85 (plug is dark , but not blackened brown) . I compared the 'Rev box cdi and stock cdi - pink wires cut on both' ; No Difference ! The stock cdi 'pink wire cut' works the same as the aftermarket $60. rev box on a stock TRX 90 with slip on and filter/jetted .

[miniquaddad90]

From my years of TRX90's the only CDI box out there that actually makes any kind of a diff is the one from Robb's Racing. I would think the Kitaco one would help (off of CRF50) but never had a chance to try one. If ever using a CRF50 CDI there will be a minor wiring change needed to make it work.