Harmen's Hints

I have copied Harmen's e-mail's straight in with no mods. As he sends more info I will add it in. Remember you use this information at your own risk.

"hello mark,
after racing 1 year in a fairly standard condition (and getting blasted on the straights) a wanted to build a better kr1 the next year . i checked everything and looked at basicly every part. luckely i already had plenty of experiance with kr1 as an mecanic and i am also an qualified engineer(ba). i made the decision to go for reliable tuning with a tune wich was not to peaky . what you want is drive from the turns and not a rebuild every race weekend.
from my experiance with heavy tuned kri's the consumption of barrels pistons and crackcases gets very expensive from about 64 bhp. getting 64 hp is fairly easy but the important bit is to have lots and lots of torque. the way for this is : - the cranks MUST be straightened within 0.03 mm , after this no more vibrations, put special grease on the seals as they will wear into the shaft otherwise. glue with locktide in the crackcases.AFTER A seizure , you MUST rebuild the crancks again as it is prone to destroy the leftside bigend. - do not get to much crackcase volume , just flow a little bit around the reedvalves. i have raced with a full tune crackcase but the engine got peaky and the strenghth is gone , after 1 seazon the bearings get loose.
i think the 70 bhp engines have these kind of set-up better to go back and losse 2 bhp but gain midrange. - DO NOT SHORTEN the barrels (standard pistons are good but heavy). the EARS are way way to thin and crack because the stresse are to high(have a look at RGV or rs125 cilinder). this is a big problem for heavy tuned machines as the stresses get bigger . to not use high compression ratio as this increases the forces even more and the engine does not respond well to it (no revs). after welding a crack the base is waisted and totally unround and cracks again after 2 races (the problem is breaking stress). try to measure the face(and get shocked) !!! welding a cilinder means a SEIZURE!!!!!! best way is to start with fresh (NEW) cilinders with the same HEIGHT . this means that there is no extra stress in the ears because of tension differences between the cinders caused by the single topend. THIS SAVES LOADS OF MONEY !!! machine the barrels by making a slightly conical axle (56.00 to 56.001) try to measure if the cilinders are straight and not unround . after 1 seazon many are crap . also after a new layer of nicasil many get unround because of the heat input . START THE SEAZON WITH GOOD CRANCKCASE AND BARRELS !!!!! othwerwise you will have problems during the seazon! pay attention to the special tightening order and make a special tool for the ones under the exhaust. you can use the topgasket again and again with a good liquid sealent (blue). - do not go for heavy compression ratio, no revs and detonation. i did have a special head with slightly higher compression ratio (will look up for you). squish 0.75 (i used 1 mm but this is to much). i used detonation rings in the cilinder as this area is quitte sloppy. after races do not ckeck the sparkplug but remove the head and let it chick by expert . check for detonation markks at the back . - i have data of cilinders as well. can give later if you wish. also dyno runs , and technical drawings of front suspension etc etc. the are obsolete so free - van kasteren exhausts in NL are the best . they give a rellly good torque , around 11500 revs and are very light. i might still have the dimensions somewere. standard is good but very heavy , gives a nice spread though - ignetion is not so very good. measured it on a scope and found it weak . heavy tunened machines have bigger spools. i raced with standard timing but you can try to shift the flyweel 5 degrees ,put on the dyno and check for detonation afterwards . suzuki RGv needs 10 degrees more spark advance(kit box already gives 5degrees)!!! - you can make big gains with the airbox . shorten the intake rubbers before the carb and change the ones in the airbox for shorter ones (-25 mm) this gives good results. no further mods in SS400 allowed, but good for many cheats as it is restrictive. - carburation : the stock needles are crap, i can look up the ones i used . do not give idle air as the engine picks up bad , idle jet must be a bit bigger as standard (42 or 45) for good pick up. set up is quitte easy . KR! can run quitte lean!!!!! check set up on the dyno if you have only little experiance! - pay attention to the base gasket . use liquid sealent as they pop out sometimes, important!!! the std. radiator is much to small for 60ish bhp KR1. use a bigger one and run at 50 C. higher running temperatures soak up many horses. i used one 50% bigger. try the breakers, also rgv is on the small side . when removing the gearbox , check the condition of the snap rings , sometimes they break after removal and it takes a long time to find the problem or get the parts(it took me 6 weeks!). clutch plates are great . mine lasted 4 seazons. the standard springs will do for 62 bhp. the ignition spool pops out once a seazon , better to make your own with more copper wound on it i race many times at ASSEN and this a is a very fast trck with flowing high speed kinks .if it performs well her then you have a good one everyweher . the standard bike was crap here the front suspesion chatered in all the banked corners and the fast ramshoek (170 kmh) was scary. it feels like a elastic frame . actually the frame is not stiff enough as some teams secretly put beams inside the spars. als the swing arm is very very light . i would like to make a bridge around it(not allowed). it took me ages to find a good set up. chassis : because of production techinqies everything is loose . make a spacer (0.35 -0.5 mm MEASURE!!!)) in the swingarm bearing . and then tighten the axle . also use spacers around all engine mounting points . no stress in the frame means that the frame copes better . watch out with tightening the headstock (critical) and the upper forkplates (cranck sometimes). USE A TORQUE WRENCH!!!! - standard rear shock has not enough bump damping , use 4 cm more riding height . the links are (lubricated?) and way to progressive . CHECK THE GAS PRESSUE . i rode with almost no staionary sag and lots of bump damping . look at the tires for marking. go for an good aftermarket shock front supension seems the limiting thing of the bike. the reason is not enough bump damping , hydraulic lock after only 60 mmm of travel and crude damping mechnistme. aftermarket springs are very progressive. 60 - 110 N/cm. 140 mm air and use the best quality oil thick 10W you can find . there are many different qualities and viscity ,no brand is the same!!! so stick to the same supplyer (ohlins seem best ROOSKENS in holland). the trick is to increase the bump damping by drilling new 3.5 mm holes and shutting the excisting one in the rods(weld) . the aluminium hydraulic locks must be machines down in size so they only work the last 10 or 5 mm or so . i had to use a lot of preload (15 mm sag and wanted to use 80 - 90 N /cm springs as the damping would function better (the springs are to progressive and give thus different damping rates as the bump speed is not constant ). the damping is a rod type , a crdridge would be 10 X better .... the best thing is to put a whole new front end of an old ns 250 inside the fork plates! but this might be cheating. MAKE THESE CHANGES AND YOU WIIL NOT REGOINISE THE BIKE AGAIN , it feels so solid and planted ! i changed it and went 3 second quicker. fastest lap time was 1.38 and this is pretty good for suck an old ratty KR1.
go and prepare a winner
Harmen "

Harmen
Do you have a dyno curve, I would be interested to see how your bike made the power. Also would you mind if I put parts of your text on the Web site?
Thanks
Mark Jordan

E -mail No 2.

"hello Mark,
yes i do have several dyno curves. compared with the stock bike the lines are parralel between 8500 and 11500 rpm just with constant more torque. because the carburation was on the rich side the first gears give a little less power compared with 4, 5 and 6th gear (cranckcases gets flooded with gasoline during idle running but very good pick up during the race) , but when the engine gets hotter the power output increases(red line ). the CO measurement equipment went all the way to 8 % ,so a smaller jetsize would even increase the power a little bit more (0.5 hp?). but on the track the engine went fine and lasted forever thanks to the rich jetting . the accerelation and topend speed was simulair with a 65-68 bhp ZXR 400 helped with a light rider (63 kg). i am sure i could have improved the power output a bit further for the next seazon(63-64 bhp?) , but i choose to go for a worldtrip .... a KR1 will never be a winner in SS400, ride a RGV or ZXR and you will understand why. my cilinders were actually quitte standard. none of the transfer ports were changed or timing increased . just main exhaust was flowed heavely(do not perform for street bikes, idele running is reduced) , the barrel undersided and general tolerances were improved (except the boost exhausts wich were 0.5 mm off , should have done it though). Current overflow geometry of NS125 cilinders are quitte different and should give much more power with improved powerband. i was afraid spending huge sums of money in high outputcilinders wich would crack anyway thus kept it quitte low profile, the power output was sufficient to keep up but the chassis needed ALL my attention!. the secondhand cilinders lasted the seazon so i gues the time spending getting the heights identical was worthwile. i need to scan the dynojet diagarms but i am very busy now, as i have just started a new job. i hope you are aware that it is not correct to compare them directly , some dyno's are 4 bhp away at a 55 bhp engine . at my dyno a standard kr1 was making 55 bhp and the winning ZXR 400 (frank Mos ) 72 bhp. the power band of ZXR is stunnning , from 8000 to 150000 the curve is like a wet dream. standard RGV&Apprilia are in the 53 to 57 bhp range and 60bhp as in your print seems a bit optimistic
ofcourse you can print it on the web site .... but don't sue me if things go wrong! all data IS correct though and personally obtained by 5 years experiance with kr1's!!!!
Harmen Lambrechts"

Harmen
..... I always worry about helping people as unless you put the engine together yourself you don't know what has been done. Once I advised somebody that you could fit the the TZ 26J pistons in a stock motor. You can as though the pistons are about 0.1mm taller than stock the stock squish clearance is very large. THis person unfortunately had a machined head and didn't check his squish - result detonation and a blown motor. Now I issue a health warning with everything. The KR engine doesn't rev as high as the RGV but from all the power curves I have seen it makes much better power in the 8000 - 10000 rpm bracket. RGV then kills the KR but the power delivery is much peakier and harder to ride. On my motor all the transfers have been widened. The bridges between ports are about 1 ~ 1.5mm. Port heights remain the same, though port timing is probably milder as the pistons are 0.1mm higher. I run a modified head to suit pistins with squish set at 0.65mm. Where the Aprilia and RGV really beat the KR is on handling. I have fitted a Tech2000 shock, and 3.5" frt dymag 5" rear dymag. The handling is still not as good as the RGV or Aprillia but it is better tahn the 400's. Hope the new job works out ok
All the best Mark J

E-mail No. 3

Hello Jordan,
i have looked into several "tuned"cilinders and i am ALWAYS very very sceptical .I did the KR1 myself and was succesfull at once but i have done several street4 and 2 strokes as well . but the kr1 is already very highly tuned and it is easy to get a unreliable engine with NO gains. luckely Frank Mos of MOBU motors (enkhuizen ) was nearby and he had plenty of experiance with tuning. his RGV used to operate at 70 odd bhp(1995). a close friend of mine bought this bike in 1999 so i quitte well know what to do with RGV as well. actually the alleged 70 bhp RGV turned out to be very worn . all cilinders were crap and he was lazy so the output was about the same as mine engine(around 60bhp) . i have ridden this particular RGV and i can tell you that it felt very peaky, from 6000 to 8500 NOTHING happened but between 8500 and 11500 the power was good above 11500 the engine almost stalled. this bike had a close ratio gearbox and was easier to keep in the powerband (when used to it) . the bike had a much better natural feel in the chassis. the suspesion settings were crap (totally worn shock and to soft at the front) but the bike responded with a surprising good controlability. a KR1 at this state would be totally unridable! the power pulses make it feel slow but the speed is the same but better controlable . the big carbs make the trottle respons a bit sloppy(first pickup at a quatre trottle) . the 28 mm of a kr1 are easy to control (jetting +trottle) and i would only go to 34 mm carbs when the output gets above 62 bhp. My KR! was made for the SS400 rules so i was not allowed to change many parts.
17 inch rubber is sooooo much better then the ancient 18 ich rubber. i also HAD to use 120/70 tyres on a 3 " rim because of the chatter problem. i tried 110/70 (the correct size) but the bike was chattering ALL the time in Assen (banked corners). i had to sort the front suspension first before changing it to correct sizes (wich i only got sorted at the last race so i never tried ...). in your case best option is to change the total front fork ( second best drill smaller 3.5 mm holes in the damper rods and weld the old 4 mm shut!) . try to get a real cartridge fork . they work 10X better because the slow speed damping is controlled. try old NS 250 forks ! I have put my bike on scales and found out that i needed at least 5 kg extra at the front to get a better weight distribution . remove the radiator expansion vessel (2 kg) and use a small bottle at the radiator (like the 250cc) at a BIG radiator. when racing the natural postion is almost IN the tank .... the bike wants more weight at the front . there is 1 guy in holland who owns a roadgoing ns250 racer with a kr1 engine installed (he races with it aswell)! my friend is still racing in the 125 cc and these bikes are much better engine and chassis wise . it is recommended to have a close look how 125/250/crossers are build (standard 125 engine does 42 bhp). good torque 125 cilinders can be found on recent NS 125 honda's. they do NOT have a power valve but they have plenty of power in the mid range (!). i think (not measured yet)the timing of the exhaust is around 195 degrees and the overflow 132 degrees . the transfer ports are NOT any wider then the KR1 and many tuners do not modify this. what tuners DO modify are the angles of the overflow ports. the overflow port on the back must be SMALL (to big on a KR1). modern overflow ports have a different geometry. the big transferports point up (around 10degrees) and the back are flat (around 0 degrees), the shape of the ports are better with more flowing angles . exhaust ports are split. excact geometry is difficult to give as there are some critical points wich need lots of attention. the water jet method is not correct as can tell you . cilinders need some turbulance at the excit for better mixing at the support ports (pronounced edges). one of the problems with 2 strokes is that it is sometimes not 100% logical what you are doing and need experince (meaning making mistakes and losing money learning so). capable tuners are not keen to give good information!!!! Tuning 125 cc racers has more to do with exhaust , ignition and the reedvalve then hacking in tye cilinders!! if you want more power with a rs125 you need to buy a expensive kit and pass $10.000 to HRC and hope for a few horses extra. i am sure a KR! would benefit from a better ingition (power +curve) and reedvalve block (tye white thing in there is restrictive. i improved them and gave them a better shape. the reedvalve matrial is pretty good . last a long time and (claimed) difficult to improve. thinner reeds (93 MX kawasaki is 0.33 mm) is a bit thinner (std=0.4) but does not last so long . personally i never tried it ,but i DO know it was used for a fast kr1 with good result. try for your selve . the MX reeds are not expensive but the STD reeds are!
try to find a old PERFORMANCE BIKE article from 1991 the give some data of 4 tuned KR1. all bikes are between 60 and 66 bhp and there are some curves as well!! the old F3 racing kit raises the barrels 0.6 mm wich means more revs. try on a fast track!. onther trick is to make exhaust rings ( and put a 3 mm shim in the exhaust . this lengthens the pipe and you can optimise the tune of the pipe to the cilinders(is critical as the mixture influences the temperature very strongly, and thuss the optimal length of the pipe is influenced ). this workes quitte well on nasty 250 cc bikes . i spoke one guy who increased the output by 5 bhp!. it is a cheap experiment with NO risks. why not use OLD copper exhaust rings they already have the correct dimesions and are easy available.
good luck,

Harmen,
Thanks, I have added all your bits to the web site as received. If there is anything you would like removed or changed please say. The modifications to the cylinders on my bike seem to work. They are not a standard tune in that I have made the rear transfers so wide that you cannot use stock pistons. The ring ends would lie in the transfer port. With the TZ pistons the ring end lies in the boost port, this doesn't cause problems because of the shallow taper in the port and because of the rotation of the engine which I think pushes the piston against the exhaust port on the compression stroke. The mods to the transfers and the head to run TZ pistons gave 59 hp. Subsequent work by Graham File resulted in about 58 hp (different dyno) but more, about 2hp, from 8000 to 10000. Drive is very good and I only loose out to the 400's coming out of very slow corners - and this is usually more to do with me either being cautious or the large step between 1st and 2nd gear on a standard box (The KR-1R runs a close ratio box but I have not been able to track one down) or I think the carburation may be a tadge lean at low RPM, i.e. coming back onto the throttle (could do with an accelarator pump?). I am due on the dyno Feb 20 so will be able to see if I can make the big 35mm carbs work. I know the 28mm carbs are easy to set up but I really would like to see if I can get the 35's to work. They are legal here as they were fitted as standard to the KR-1R and KR-1S C3A (though neither of these were officially imported into the UK). The rules in F400 in the UK seem very lax at the moment - none of the F400 championships are high profile so nobody is to fussed if things are changed a bit. Originally you could only race bikes officially imported now it is anything so you get a good mix of bikes. Mainly it is ZXR400, FZR 400, NC35 then a few CBR and GSXR. For two strokes it is mainly Aprilia then RGV , KR and a few NS250 normal and SP. There are also one or two TZ250. ..... On the KR and NC30 a lot of people fit 17" rear wheels, from the RGV and NC35 respectively. Quite a few have fitted Dymag wheels as I have done. The ZXR 400's also fit the flat slide carbs found on the SP model (again this was never imported officially in the uk)...... As long as no one bike dominates then nobody complains - it also costs £250 to complain about a 4 stroke, £150 about a two stroke and £400 to complain about fuel!! I would say the biggest difference to the bike has been made by the following in order of benefit

17" Rear and running Dunlop KR364
Fitting 3.5" frt and 5" rear dymags
The ride height adjuster onthe new rear shock
forced air induction
Initial porting
The new rear shock
The.... subsequent tuning

My weight distribution no rider is currently 51.5% frt and 48.5% rear which I think is about right. I already have a little 125 expansion bottle on the radiator, and have removed quite a bit of the bike that is not need to lose weight. In the class you do not need to maintain starting or charging capability though I still run a kick start as it is convenient. I have always wondered if a crosser barrel from 1991/2 would fit. They are the same bore and stroke and use the same reed block? I have the performance bike article - bit disappointed by the quality of the dyno curves. there is also another article I have seen but do not have in Sept 1991 Superbike on tuning and racing the KR. I will report back after our dyno session. I have stock, boysen, Hy-Tecj and plain fibreglass reeds to try........ I do not expect reeds to last long. We also have several expansions to try out.
All the best
Mark Jordan

E-mail No 4

hello Mark,
the problem of bad pick -up is common. the trick is to use bigger pilot jets and close the idle mixture screw, make sure the carbs are perfectly sychronized. standard pilot jet is 40 but i used a very rich set - up 45 with closed mixture screw. on the dynojet bench this looks awful at low gears but in reality it is perfect (crackcases gets flooded during warm -up) . other people used 42 or 45 but always in combination with closed mixiture screws. RGV have a very advanced system to control this , they shut of the tube controling the mixture screws while reving high , thus improving pick up but still have nice idle running. especially smoothing the main exhaustport increases the need for this while the fresh mixture during idle running can flow freely to the exhaust. in holland with it's very strict SS400 rules the ZXR 400 were dominent. the basis is very good and for very few money it is possible to create a competitive bike . people who switches over were also very impressed with the chassis. they are easy to ride , tune and reliable. although they sometimes like to kick out a conrod thuss destroying the engine and making a ruin of the owners financial postion . because of the high amount of street tracks with its slow corners the 4 strokes are a better choice . but personally i favor the 2 strokes. must admit that i wiched i started with a RGV . the basis is much better anf 65 reliable bhp are easy to get WITH a wide spread of power . the exhaust design is simply much better (although the power valves material is crap) . when raising the main exhaust of the kr1 you destroy the midrange . try measuring 2 cilinders and see that the tolerances in the cilinders are very BIG . often the ports are 0.5 mm off. making the timing identical is quitte easy and improves the power band. i hope you get a good session and get some useful BHP. i am very interrested in the results!!!! standard tolerance of a dyno is 3% so for a 60 bhp engine 4 bhp! and the correction factor(temp /desity &pressure) is a little but dubious. i used 4 star petrol because i had no problems with detonation . i know it is a cheap cheat (not allowed) with 250 CC as Elf racing fuel is rather pricy (understatement). i saw some curves with Elf and other racing fuels and was amazed , the effect on the midrange is sometimes very strong top end with a zxr 400 was about +2 bhp (from 70 to 72) . ALL top 4 stroke bikes in holland use ELF or simular fueles but they are also heavy sponsored . almost all 125 and 250 cc bikes run on this trick fuel as it is easy to set-up. for Elf you have a range of 5 jeys between seizure and to fat (won't run) but for 3 star only 2 or 3 with a nasty Appilia(92 bhp) or highly tuned honda (85 bhp).
good luck harmen

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This document maintained by mark@teamsparrow.fsnet.co.uk.
Material provided by Harmen Lambrechts - 2002