bigbird2

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These are the calcs I used to come up with the 1/3 reduction in CR. Please check and let me know if you agree/disagree? THANKS 72.5 Bore mm 36.25 Radius mm 36.25 Times Radius mm 1314 Radius Sq. 3.14 Times Pi 4130 Pi R Sq = area in sq mm 41 Area of top of bore hole in sq cm 0.3 3mm Spacer height/thickness in cm 12 3 mm spacer hole Voulume in CCs 270 Beta Displacement in CCs 11.4 Divide by Beta Stock CR 24 = Beta Stock Chamber Vol CCs 36 Expanded Chamber Vol in CCs 7.5 NEW CR (Displacement / Expanded Vol) -34% Change in CR

Don't have a picture BUT a head spacer would have exactly the same shape as a head gasket - just thicker. You may be right about the numerical CR calc difference? However, I'd guess that earlier CRs were much lower due to the limitations of air cooling if nothing else. My 250 Ossa MAR was so easy to kick that my 105 lb wife could start it. However it does have a looooong kick start lever.

Thanks Again for your input. I don't even actually have the bike yet but have a friend with the same bike that I have kicked a few times. I can start it but it is sort of marginal and I think it would get very annoying at best on a hot day when I'm tired, etc. I don't need the power of the 270 so I'm thinking why not detune it and make it easy to kick (or go the 200 route) Re: The 30% reduction in CR IS a lot but Adrian said it had worked well for several of his customers. I've found a 2008 250 manual that lists the CR at 11:4 to 1 - WOW --- I think the CRs on the early 70s trials bike were around 6:1

THANKS to both of you. I talked to Adrian at Lewisport and learned that he has successfully used as many as 3 of the 1 mm head spacers he had made for some earlier model Gas Gas 2t 250-300 bikes to tame them and make them start easier. 3 mm looks like it would lower the compression ratio on my 270 by about 1/3.

Yes but I was having trouble finding one this was a GREAT deal.

I JUST made a deal to get a one and now I am on a quest to make it easier to kick start. I'm OLD!!! I had a thread on this on the General board - before I'd settled on a specific bike (and because I have a gal friend with the same issue) but thought you folks on this board might have more good ideas on this specific bike. I'm thinking of retarding the timing - maybe 5 degrees??? I'm also thinking of adding base gasket(s) to raise the cyl - maybe 1mm to 3mm??? OR I was thinking of making a 2mm to 3mm replica of the head gasket out of aluminum as another way of increasing the combustion chamber volume without changing port timing??? Do you know anything about how difficult this would be to make? Also would I want to used a standard head gasket on BOTH sides if it? I guess I could also grind some metal out of the dome part of the cylinder head which would avoid messing up the squish area around the edges and not affect the port timing - but of course this is not reversible. Although getting it to tuck in might be a problem - the idea of lengthening the kick starter seems like it would help too? Anyone know of a source for a broken on I could get to try it on? Any thoughts you have will be appreciated.

THANKS for all the good input! I JUST bought a 2007 Beta 270! So now I'll be embarking on making it easier to kick. I will definitely retard the timing - one guy I talked to suggested 5 degrees - does anyone have other advice? I will also either add base gasket(s) or try to make a head spacer. IF I do the head spacer out of say 2mm aluminum - would I want to have a normal head gasket on each side of it? Adrian at Lewisport told me they had added head spacers to Gas Gas big 2t bikes of 1mm to 3mm with success. Although getting it to tuck in might be a problem - the idea of lengthening the kick starter seems like it would help too? If anyone has more ideas/input it will be appreciated. I'll report back after I've tried some stuff.

In my search for easy starting 2t trials bikes some have suggested motor mods to ease kick starting. The items that have come up so far are lowering compression and/or adding a compression release for starting (like was used in the 70s as a brake assist) by adding another hole (like a spark plug hole) in the head? Is this even possible with water cooled motors? Does anyone have any knowledge or experience with these mods? OR any other ideas? I'm interested in anything but wondered about the "optimum" compression ratio to get a good balance between starting ease and maintain sufficient power? And/or ideas on how low one can go without really messing up the motor performance? Also pros and cons of just adding to base gasket thickness VS removing metal from the dome of the combustion chamber in the head (to avoid messing up the "squish" area around the perimeter of the pistion/head? Also does anybody know of a trials bike that one could add an e-start from a related enduro motor to? THANKS for any help!

Well I just got the top part of the cylinder head off and found what at least some of the problem is. The fiber cam chain guides are destroyed and the red stuff is all over inside the top head, etc. Thus the cam chain is very loose and the cam can be rotated quite a bit with the crank stopped. SO now I'd appreciate any help you can offer on what parts I will need to fix this (besides the obvious cam chain guides). Also will I be able to insert the new cam chain guides without removing the cylinder head and/or cylinder, etc.? Is there a way to determine if the cam chain and gears are OK? The cam chain can not be significantly pulled away from the cam gear at 12:00 o'clock if the chain is held against the gear at 3:00 and 9:00 o'clock - so my initial assumption is it is OK. Right now the engine is still in the frame (but dropped down a little to get the cam cover off) with all the wires and carb, etc. attached and with the swing arm bolt still installed. Will I need to remove it? OR can I get the side cover/case off and the new cam guides installed with the engine still in place? Thanks again for your help.

Well I tired the really easy fix of just doing the cam chain tensioner check but no luck there. I now have the decompression spring, etc. so will tackle that next. I'm a little confused by your statement about setting the TDC per the service manual? The valve gear section 4.17.2 tells one to: Take care to time up the camshaft properly. The crankshaft is locked at TDC by the special bolt which was fitted earlier (see 4.11). Position the camshaft so that the timing mark (A) is horizontal on the exhaust valve side. When I go to section 4.11 it show a bolt going into the gear box area from the front of the engine and says: Lock the crankshaft at TDC using the appropriate bolt (7), However it never says anything about removing the bolt and the parts manual show the bolt as a standard part? Are you telling me I need to do this locking of the crankshaft? And IF SO am I supposed to get a LONGER bolt to do the locking and then put the standard bolt that I removed back in afterwards so the crank is no longer locked? OR are you just telling me to line the cam gear mark up with the front of the head and mark the chain then hold it up and get it back onto the cam gear in the same place? Sorry for all the questions - but I really appreciate your help!!! It also looks like you are telling me I don't need to remove the engine (but rather can just drop the front down)! YEA! THANKS AGAIN!!!!

Thanks for all the replies! It seems that most are recommending the smaller displacement 2ts and that may indeed be my best bet. However, I was wondering if there are any particular brand or model ~ 250cc 2ts that are generally easier to kick than others due to things like lever length, placement, gear reduction, etc? Also how about things like a compression release (like I had many years ago on my 1970s 2ts (when they didn't have good waterproof brakes)? Again all ideas appreciated.

I am interested in getting a used modern trials bike but am concerned that some of them may not be easy for an OLD guy like me to start - particularly when I'm tired and the bike has been dropped, etc. I have e-start on my trail and enduro bikes for this reason. I recently saw a 2008 Beta 270 Rev 3 for sale that sounded reasonable. I asked a friend that has a bike like that about it and he told me it is rather difficult to kick start - short kick lever requiring lots of force to spin the motor. So my question is what brands and models of used trials bikes are the EASIEST to start, hot or cold? My preference is for a 2 stroke due to the lighter weight, etc. but would consider a 4 stroke if there are no easy starting 2 strokes. THANKS for any help on this.

jimg - Thanks for the reply. I will do as you suggest before going after the spring replacement. Maybe I'll be really lucky? The only reason I didn't jump on it the first time is that I ASSUMED that since my noise was loud and sudden that it was more likely the spring. BUT your idea is certainly worth a shot and basically free! Thanks Again.

You guys are great! Responses from England Scotland NZ Michigan USA! Keep them coming as I need all the help I can get!

WOW! I'm impressed by the responses! Thanks Folks! I got sidetracked for a few days with a problem with another bike but now I'm gonna try the Beta. Hopefully my problem is the spring for the decompressor weight. The noise appeared suddenly and sounds BAD. I had to ride the bike for a mile or so with the noise and tried not to rev it too much. From looking at the manual - I THINK I can replace the spring without getting into the bottom of the engine? Is it possible to get the cam out and back in without messing with the water pump or even removing the bottom part of the cylinder head? It seems like I MIGHT be able to just take the top of the cylinder head off then slip the bearings off the cam then get the cam out to replace the decompressor spring. If I marked where the cam sprocket teeth mate to chain, MAYBE I could reassemble it back the same way to avoid having to do the locking of the crank at TDC routine? IF this plan is workable and it is the spring - I don't see any parts other than the spring that I'd need - unless it is likely that the weight is damaged? This assumes I could reuse the O-rings that are on the little covers one uses to check and adjust the valves, etc. I'd appreciate any guidance you can offer. I'm not too cheap to by any parts you think I'll need. Just trying to keep it as simple as possible. I'm reasonably competent at this kind of stuff BUT sure don't want to get into it any deeper than necessary. THANKS AGAIN!

My 2009 300 4t sounds BAD. I haven't done any investigation yet to determine what is wrong but it is making knocking sounds so probably NOT trivial. Does anyone have recommendations on repair service available locally OR that I could ship the motor to (assuming it is a serious problem)? I live in Frederick Maryland. There is a local dealer but he has never been inside one of these 4t engines. Thanks for any help!

Stolen Bikes have been RECOVERED!

Stolen Bikes have been RECOVERED!!!

$10,000 REWARD FOR INFO LEADING TO RETURN OF 3 VERY UNUSUAL HIGHLY MODIFIED OFF-ROAD MOTORCYCLES - STOLEN 7/6/2013 from Braddock Heights, MD 21703 Contact Sam Jones 301-788-8848 $5,000 - 2007 KTM 200 XCW - VIN V8KXWH2347M167515 Color Orange Vanity Tag "KTMXCW" with 2013 electric start motor installed - engine number 035243515 and extensive mods and upgrades including: Gnarley Pipe with FMF Muffler & Spark Arrester Revlock Auto Clutch Left Hand Rear Brake Scotts Steering Stabilizer X Bushing in Rear Swingarm Shortened Ohlins TTX in Rear Enduro Engineering Seat Trail Tech Vector Speed/ODO Carbon Fiber Skidpan Small Front and Rear Fender Bags Aluminum Grab Handle on Right Rear $3,000 - 2009 BETA 300 EVO 4T - VIN ZD3T602010500014 (VIN Not Legible) Engine ZD3E84 0920060 with extensive mods and upgrades including: Long Ride Kit (1.1 Gallon Aux Tank & Seat) Scotts Stabilizer - mounted on aluminum block in front of steering tube BBR Seat at Normal Trail Ride Height 16" Rear Wheel (vs original 18") EFM Auto-Clutch with working clutch lever LHRB - Left Hand Rear Brake Full Knobys 21" Front & 16" Rear 6" Rise Jitsie Handlebars Acerbis Plastic Barkbusters $2,000 - 2007 BETA Rev 80 2t with extensive mods and upgrades including: Rekluse Auto Clutch LHRB - Left Hand Rear Brake Scotts Stablilzer BBR Seat at Normal Trail Ride Height 21" Front Knobby 3.50-18" Low Profile Rear Knobby

$10,000 REWARD FOR INFO LEADING TO RETURN OF 3 VERY UNUSUAL HIGHLY MODIFIED OFF-ROAD MOTORCYCLES - STOLEN 7/6/2013 from Braddock Heights, MD 21703 USA Contact Sam Jones 301-788-8848 $5,000 - 2007 KTM 200 XCW - VIN V8KXWH2347M167515 Color Orange Vanity Tag "KTMXCW" with 2013 electric start motor installed - engine number 035243515 and extensive mods and upgrades including: Gnarley Pipe with FMF Muffler & Spark Arrester Revlock Auto Clutch Left Hand Rear Brake Scotts Steering Stabilizer X Bushing in Rear Swingarm Shortened Ohlins TTX in Rear Enduro Engineering Seat Trail Tech Vector Speed/ODO Carbon Fiber Skidpan Small Front and Rear Fender Bags Aluminum Grab Handle on Right Rear $3,000 - 2009 BETA 300 EVO 4T - VIN ZD3T602010500014 (VIN Not Legible) Engine ZD3E84 0920060 with extensive mods and upgrades including: Long Ride Kit (1.1 Gallon Aux Tank & Seat) Scotts Stabilizer - mounted on aluminum block in front of steering tube BBR Seat at Normal Trail Ride Height 16" Rear Wheel (vs original 18") EFM Auto-Clutch with working clutch lever LHRB - Left Hand Rear Brake Full Knobys 21" Front & 16" Rear 6" Rise Jitsie Handlebars Acerbis Plastic Barkbusters $2,000 - 2007 BETA Rev 80 2t with extensive mods and upgrades including: Rekluse Auto Clutch LHRB - Left Hand Rear Brake Scotts Stablilzer BBR Seat at Normal Trail Ride Height 21" Front Knobby 3.50-18" Low Profile Rear Knobby

This FrankenBeta is terrific. I've now made the following ADDITIONAL mods and the bike is even better. Substituted Garmin Montana for the eTrex Added an EFM Auto Clutch This is a great improvement for me (because all my other bikes have auto-clutch and I was having trouble rememberiring to use the Beta clutch. ALSO the makes the gap between 3rd and 4th a non problem as, within reason, you can use 4th at very low speeds Added a Left Hand Rear Brake (which is in addition to the normal foot brake) This provides great flexibility and works well when riding sitting down (where it is hard to use the foot brake) Added SPIKED knobby tires for use in winter on ice, snow and wet roots and logs. Tried them out about 10 days ago and was AMAZED at the traction. I was never even able to use their full potential becasue I didn't have the confidence to reley on them. You can hit a slick log at 60 degrees and it just goes right over - no drama. Also icy trails are no problem.

I'm NOT much of a trials rider buy have done quite a bit of experimentation in the process of modifying my 2009 4t suspension for trail riding. My advice would be: Get stiffer springs (by the way increaseing Pre-Load does NOT make a spring stiffer just sets the ride height up higher). Increase the damping on the rear shock to damp the rebound of the stiffer spring (there is quite a bit of range available). Incresed the viscosity of the oil in the right fork only. This will increase compression damping and provide an increased range of rebound damping to control the stiffer springs.

I think the Regulator on my 2009 300 4t is bad. Stator is good and fan and fan swithch are good but fan doesn't work. I have ordered the regulator. Question is - can I run the fan and fan swithch directly off of the unregulated stator output? I don't have any lights, horn, etc. so I think all the stator aux power circuit drives is the fan? OR - Does it also drive the fuel valve? If so why does it run without the valve switched to ON? Also - Does anyone know where I can find a legible wiring diagram? The one in the manual is just too faint to read on the computer or to print. Thanks for any help!

Thanks for the reply. I have one large hose that goes from the engine to the air box (crankcase breather?) I also have a small hose that goes from ? forward into the air box. These 2 hoses use all the hose holes in the airbox. Thus I don't THINK the hoses I'm asking about are airbox related?